Gemological, Spectral and Chemical Features of Canary Yellow Chrysoberyl

Abstract

In this study, seventeen faceted gem-quality chrysoberyls exhibiting an attractive canary yellow color were investigated using a variety of gemological, spectral, and chemical methods. Microscopic observation revealed the presence of distinct growth lines and inclusions, including CO2 fluids, carbon, and crystals of mineral such as calcite, quartz, sillimanite, and mica, identified by the Raman spectrum. The FTIR spectra showed the characteristic peaks of 2405 and 2160 cm−1 and a 3223 cm−1 peak in all samples, which can be accompanied by the 3112 cm−1 shoulder, 3301, and 3412 and 3432 cm−1 peaks. The UV-Vis spectra showed an Fe-related peak at 440 nm, along with the 650–660 nm band and the absorption band in the blue zone of visible light. Chemical analyses via EDXRF showed a composition poor in V and Cr and rich in Fe. The spectral and chemical results could help explain the origin of the canary yellow color, which originates from the abundant amount of Fe with very little influence from Cr and V.

Full text

Citation: Gao, Y.; Li, X.; Cheng, Y.;
Huang, T.; Li, K.; Xu, B.; Tang, R.
Gemological, Spectral and Chemical
Features of Canary Yellow
Chrysoberyl. Crystals 2023,13, 1580.
https://doi.org/10.3390/
cryst13111580
Academic Editor: Sergey
V. Krivovichev
Received: 2 October 2023
Revised: 5 November 2023
Accepted: 7 November 2023
Published: 11 November 2023
Copyright: © 2023 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
crystals
Article
Gemological, Spectral and Chemical Features of Canary
Yellow Chrysoberyl
Yujie Gao 1, Xu Li 2,3, Yansheng Cheng 4, Tiantian Huang 1,*, Kongliang Li 5, Bo Xu 6,7 and Ruobin Tang 8
1Guild Gem Laboratories, Shenzhen 518020, China; peter.gao@guildgemlab.com
2Shenzhen Academy of Inspection and Quarantine, Shenzhen 518010, China; gypzh@customs.gov.cn
3The Testing and Technology Center for Industrial Product of Shenzhen Customs, Shenzhen 518067, China
4
China National Accreditation Service for Conformity Assessment, Beijing 100062, China; chengys@cnas.org.cn
5College of Geology and Construction Engineering, Anhui Technical College of Industry and Economy,
Hefei 230051, China; 1207013@ahiec.edu.cn
6
State Key Laboratory of Geological Processes and Mineral Resources, School of Gemmology, China University
of Geosciences, Beijing 100083, China; bo.xu@cugb.edu.cn
7The Beijing SHRIMP Center, Chinese Academy of Geological Sciences, Beijing 100037, China
8Independent Researcher, Chengdu 610000, China; tangrb@scjewel.club
*Correspondence: candice.huang@guildgemlab.com
Abstract:
In this study, seventeen faceted gem-quality chrysoberyls exhibiting an attractive canary
yellow color were investigated using a variety of gemological, spectral, and chemical methods.
Microscopic observation revealed the presence of distinct growth lines and inclusions, including CO
2
fluids, carbon, and crystals of mineral such as calcite, quartz, sillimanite, and mica, identified by the
Raman spectrum. The FTIR spectra showed the characteristic peaks of 2405 and 2160 cm
−1
and a
3223 cm
−1
peak in all samples, which can be accompanied by the 3112 cm
−1
shoulder, 3301, and
3412 and 3432 cm
−1
peaks. The UV-Vis spectra showed an Fe-related peak at 440 nm, along with the
650–660 nm band and the absorption band in the blue zone of visible light. Chemical analyses via
EDXRF showed a composition poor in V and Cr and rich in Fe. The spectral and chemical results
could help explain the origin of the canary yellow color, which originates from the abundant amount
of Fe with very little influence from Cr and V.
Keywords: chrysoberyl; Raman; trace elements; CIELab
1. Introduction
The chrysoberyl crystal lattice is composed of oxygen ions organized in a hexagonal
close-packed array (Figure 1), with beryllium and aluminum ions filling the octahedral in-
terstices between them [
1
–
3
], which gives chrysoberyl a comparatively high Mohs hardness
of 8.5, making it one of the hardest gemstones after diamonds, rubies, and sapphires.
Chrysoberyl is a mineral that has been known and used for centuries. It was first
described by the Swedish mineralogist Axel Frederik Cronstedt in 1758, and the name
comes from the Greek words “chrysos” meaning golden, and “beryllos” meaning beryl [
4
].
He named the mineral “chrysoberyl” in honor of its golden hue.
Some varieties of chrysoberyl exhibit the chatoyancy, or cat’s eye effect, which is
brought on by parallel needle-like inclusions within the crystal structure, usually made
of rutile or hematite. Due to the way these imperfections reflect light, a bright line that
resembles a cat’s eye appears across the gemstone’s surface [5].
Alexandrite, one of the most well-known types of chrysoberyl, was initially found in
the Ural Mountains of Russia in the early 19th century. It was given the name Alexandrite
after Czar Alexander II, who turned 18 on the day it was founded [
6
]. Its ability to change
color under various lighting conditions—appearing green in daylight and reddish-purple
in incandescent light—makes alexandrite highly prized [
7
]. Currently, alexandrite can be
Crystals 2023,13, 1580. https://doi.org/10.3390/cryst13111580 https://www.mdpi.com/journal/crystals

Crystals 2023,13, 1580 2 of 17
found in many localities, including Russia, Tanzania, Zimbabwe, Brazil as well as Sri Lanka,
etc. [
5
,
6
,
8
–
10
]. Recently, a study was applied to the originated determination of alexandrite
from various localities owing to their important economic value in the gem trade [11].
Crystals 2023, 13, x FOR PEER REVIEW 2 of 18
Figure 1. The crystalline structure of chrysoberyl includes beryllium, aluminum, and oxygen atoms
[1].
Alexandrite, one of the most well-known types of chrysoberyl, was initially found in
the Ural Mountains of Russia in the early 19th century. It was given the name Alexandrite
after Czar Alexander II, who turned 18 on the day it was founded [6]. Its ability to change
color under various lighting conditions—appearing green in daylight and reddish-purple
in incandescent light—makes alexandrite highly prized [7]. Currently, alexandrite can be
found in many localities, including Russia, Tanzania, Zimbabwe, Brazil as well as Sri
Lanka, etc. [5,6,8–10]. Recently, a study was applied to the originated determination of
alexandrite from various localities owing to their important economic value in the gem
trade [11].
Chrysoberyl has been used throughout history as a gemstone and for decorative pur-
poses. In ancient times, it was believed to have protective properties and was often worn
as an amulet or talisman. Today, it is still highly valued as a gemstone due to its beauty
and durability and is often used in high-end jewelry. In this article, the common chryso-
beryl refers to chrysoberyl that does not exhibit color changing or chatoyance effect. Even
though they share an identical crystalline structure and belong to the same mineral [12],
the alexandrite and cat’s eye possess a high reputation and command much higher prices
than the common chrysoberyl in the gem trade.
However, the trend of undervaluation of the common chrysoberyl has been turned
around as much more chrysoberyl of aractive color has entered the gem market. In recent
years, green chrysoberyl has entered the market and gained considerable aention, show-
ing a strong rise in popularity [13]. These green varieties usually exhibit a green hue of
medium to high saturation owing to the trace amount of vanadium within the crystalline
structure. Meanwhile, the chrysoberyl of yellow color, resembling the canary yellow dia-
mond, also entered the gem market, causing a warming current in the trade.
In this study, we applied various methods to investigate a parcel of 17 canary yellow
chrysoberyl samples: the investigations included their gemological, spectral, and chemical
features, with the aim of providing more information about this gem variety and advanc-
ing our understanding with more reliable data.
2. Materials and Methods
In this study, we have selected 17 pieces of faceted gem-quality chrysoberyl material
that were purchased from a gem dealer to investigate their gemological, spectral, and
chemical features by a variety of methods (Table 1). The dealer did not specify the geo-
graphic or geological origin of the samples used in this study. Using Munsell card, the
colors range from greenish yellow to pure yellow with medium to high saturation, and all
the samples are transparent and of good clarity. These kind of yellow chrysoberyl samples
may come from many countries, including Brazil, Sri Lanka, India, Madagascar, Australia
Figure 1.
The crystalline structure of chrysoberyl includes beryllium, aluminum, and oxygen
atoms [1].
Chrysoberyl has been used throughout history as a gemstone and for decorative
purposes. In ancient times, it was believed to have protective properties and was often
worn as an amulet or talisman. Today, it is still highly valued as a gemstone due to its beauty
and durability and is often used in high-end jewelry. In this article, the common chrysoberyl
refers to chrysoberyl that does not exhibit color changing or chatoyance effect. Even though
they share an identical crystalline structure and belong to the same mineral [
12
], the
alexandrite and cat’s eye possess a high reputation and command much higher prices than
the common chrysoberyl in the gem trade.
However, the trend of undervaluation of the common chrysoberyl has been turned
around as much more chrysoberyl of attractive color has entered the gem market. In
recent years, green chrysoberyl has entered the market and gained considerable attention,
showing a strong rise in popularity [
13
]. These green varieties usually exhibit a green
hue of medium to high saturation owing to the trace amount of vanadium within the
crystalline structure. Meanwhile, the chrysoberyl of yellow color, resembling the canary
yellow diamond, also entered the gem market, causing a warming current in the trade.
In this study, we applied various methods to investigate a parcel of 17 canary yellow
chrysoberyl samples: the investigations included their gemological, spectral, and chemical
features, with the aim of providing more information about this gem variety and advancing
our understanding with more reliable data.
2. Materials and Methods
In this study, we have selected 17 pieces of faceted gem-quality chrysoberyl material
that were purchased from a gem dealer to investigate their gemological, spectral, and chem-
ical features by a variety of methods (Table 1). The dealer did not specify the geographic or
geological origin of the samples used in this study. Using Munsell card, the colors range
from greenish yellow to pure yellow with medium to high saturation, and all the samples
are transparent and of good clarity. These kind of yellow chrysoberyl samples may come
from many countries, including Brazil, Sri Lanka, India, Madagascar, Australia and so
on [
14
]. Samples in this study are from gem dealers without specific origins, since the origin
is not an add-value parameter in the gem trade currently, while color comes first when
evaluating the chrysoberyl. The weight ranges from 1.97 to 7.43 carats, and the details of
all the samples can be found in Table 1.

Crystals 2023,13, 1580 3 of 17
Table 1. Basic information of the seventeen chrysoberyl samples investigated in this study.
No. Weight Shape Dimensions Sample
Photo No. Weight Shape Dimensions Sample
Photo
G23001-1 4.05 ct Triangular 9.15 ×9.23
×6.57 mm
Crystals 2023, 13, x FOR PEER REVIEW 3 of 18
and so on [14]. Samples in this study are from gem dealers without specific origins, since
the origin is not an add-value parameter in the gem trade currently, while color comes
first when evaluating the chrysoberyl. The weight ranges from 1.97 to 7.43 carats, and the
details of all the samples can be found in Table 1.
Table 1. Basic information of the seventeen chrysoberyl samples investigated in this study.
No. Weight Shape Dimensions Sample Photo No. Weight Shape Dimensions Sample Photo
G23001-1 4.05 ct Triangular 9.15 × 9.23 ×
6.57 mm 1G23001-10 3.46 ct Pear 11.28 × 7.93 ×
5.80 mm
G23001-2 4.51 ct Pear 15.82 × 7.68 × 5.07
mm G23001-11 2.79 ct Pear 10.74 × 7.71 ×
5.12 mm
G23001-3 5.21 ct Pear 14.33 × 8.03 × 6.69
mm G23001-12 7.43 ct Pear 14.01 × 9.45 ×
8.09 mm
G23001-4 1.97 ct Pear 12.00 × 5.90 × 4.06
mm G23001-13 2.09 ct Oval 8.96 × 6.91 × 4.65
mm
G23001-5 4.92 ct Pear 14.98 × 7.98 × 6.03
mm G23001-14 2.12 ct Oval 8.94 × 6.95 × 4.73
mm
G23001-6 2.10 ct Pear 11.96 × 6.00 × 4.45
mm G23001-15 6.00 ct Oval 10.75 × 9.84 ×
7.48 mm
G23001-7 2.87 ct Pear 13.76 × 6.82 × 4.33
mm G23001-16 4.16 ct Oval 10.68 × 8.46 ×
6.34 mm
G23001-8 3.05 ct Pear 13.72 × 6.80 × 4.83
mm G23001-17 3.09 ct Cushion
9.83 × 7.76 × 4.98
mm
G23001-9 4.81 ct Pear 15.01 × 8.00 × 5.97
mm
G23001-10 3.46 ct Pear 11.28 ×7.93
×5.80 mm
Crystals 2023, 13, x FOR PEER REVIEW 3 of 18
and so on [14]. Samples in this study are from gem dealers without specific origins, since
the origin is not an add-value parameter in the gem trade currently, while color comes
first when evaluating the chrysoberyl. The weight ranges from 1.97 to 7.43 carats, and the
details of all the samples can be found in Table 1.
Table 1. Basic information of the seventeen chrysoberyl samples investigated in this study.
No. Weight Shape Dimensions Sample Photo No. Weight Shape Dimensions Sample Photo
G23001-1 4.05 ct Triangular 9.15 × 9.23 × 6.57
mm G23001-10 3.46 ct Pear211.28 × 7.93 ×
5.80 mm
G23001-2 4.51 ct Pear 15.82 × 7.68 × 5.07
mm G23001-11 2.79 ct Pear 10.74 × 7.71 ×
5.12 mm
G23001-3 5.21 ct Pear 14.33 × 8.03 × 6.69
mm G23001-12 7.43 ct Pear 14.01 × 9.45 ×
8.09 mm
G23001-4 1.97 ct Pear 12.00 × 5.90 × 4.06
mm G23001-13 2.09 ct Oval 8.96 × 6.91 × 4.65
mm
G23001-5 4.92 ct Pear 14.98 × 7.98 × 6.03
mm G23001-14 2.12 ct Oval 8.94 × 6.95 × 4.73
mm
G23001-6 2.10 ct Pear 11.96 × 6.00 × 4.45
mm G23001-15 6.00 ct Oval 10.75 × 9.84 ×
7.48 mm
G23001-7 2.87 ct Pear 13.76 × 6.82 × 4.33
mm G23001-16 4.16 ct Oval 10.68 × 8.46 ×
6.34 mm
G23001-8 3.05 ct Pear 13.72 × 6.80 × 4.83
mm G23001-17 3.09 ct Cushion
9.83 × 7.76 × 4.98
mm
G23001-9 4.81 ct Pear 15.01 × 8.00 × 5.97
mm
G23001-2 4.51 ct Pear 15.82 ×7.68
×5.07 mm
Crystals 2023, 13, x FOR PEER REVIEW 3 of 18
and so on [14]. Samples in this study are from gem dealers without specific origins, since
the origin is not an add-value parameter in the gem trade currently, while color comes
first when evaluating the chrysoberyl. The weight ranges from 1.97 to 7.43 carats, and the
details of all the samples can be found in Table 1.
Table 1. Basic information of the seventeen chrysoberyl samples investigated in this study.
No. Weight Shape Dimensions Sample Photo No. Weight Shape Dimensions Sample Photo
G23001-1 4.05 ct Triangular 9.15 × 9.23 × 6.57
mm
G23001-10 3.46 ct Pear 11.28 × 7.93 ×
5.80 mm
G23001-2 4.51 ct Pear 15.82 × 7.68 × 5.07
mm
G23001-11 2.79 ct Pear 10.74 × 7.71 ×
5.12 mm
G23001-3 5.21 ct Pear 14.33 × 8.03 × 6.69
mm
G23001-12 7.43 ct Pear 14.01 × 9.45 ×
8.09 mm
G23001-4 1.97 ct Pear 12.00 × 5.90 × 4.06
mm
G23001-13 2.09 ct Oval 8.96 × 6.91 × 4.65
mm
G23001-5 4.92 ct Pear 14.98 × 7.98 × 6.03
mm
G23001-14 2.12 ct Oval 8.94 × 6.95 × 4.73
mm
G23001-6 2.10 ct Pear 11.96 × 6.00 × 4.45
mm
G23001-15 6.00 ct Oval 10.75 × 9.84 ×
7.48 mm
G23001-7 2.87 ct Pear 13.76 × 6.82 × 4.33
mm
G23001-16 4.16 ct Oval 10.68 × 8.46 ×
6.34 mm
G23001-8 3.05 ct Pear 13.72 × 6.80 × 4.83
mm
G23001-17 3.09 ct Cushion
9.83 × 7.76 × 4.98
mm
G23001-9 4.81 ct Pear 15.01 × 8.00 × 5.97
mm
G23001-11 2.79 ct Pear 10.74 ×7.71
×5.12 mm
Crystals 2023, 13, x FOR PEER REVIEW 3 of 18
and so on [14]. Samples in this study are from gem dealers without specific origins, since
the origin is not an add-value parameter in the gem trade currently, while color comes
first when evaluating the chrysoberyl. The weight ranges from 1.97 to 7.43 carats, and the
details of all the samples can be found in Table 1.
Table 1. Basic information of the seventeen chrysoberyl samples investigated in this study.
No. Weight Shape Dimensions Sample Photo No. Weight Shape Dimensions Sample Photo
G23001-1 4.05 ct Triangular 9.15 × 9.23 × 6.57
mm
G23001-10 3.46 ct Pear 11.28 × 7.93 ×
5.80 mm
G23001-2 4.51 ct Pear 15.82 × 7.68 × 5.07
mm
G23001-11 2.79 ct Pear 10.74 × 7.71 ×
5.12 mm
G23001-3 5.21 ct Pear 14.33 × 8.03 × 6.69
mm
G23001-12 7.43 ct Pear 14.01 × 9.45 ×
8.09 mm
G23001-4 1.97 ct Pear 12.00 × 5.90 × 4.06
mm
G23001-13 2.09 ct Oval 8.96 × 6.91 × 4.65
mm
G23001-5 4.92 ct Pear 14.98 × 7.98 × 6.03
mm
G23001-14 2.12 ct Oval 8.94 × 6.95 × 4.73
mm
G23001-6 2.10 ct Pear 11.96 × 6.00 × 4.45
mm
G23001-15 6.00 ct Oval 10.75 × 9.84 ×
7.48 mm
G23001-7 2.87 ct Pear 13.76 × 6.82 × 4.33
mm
G23001-16 4.16 ct Oval 10.68 × 8.46 ×
6.34 mm
G23001-8 3.05 ct Pear 13.72 × 6.80 × 4.83
mm
G23001-17 3.09 ct Cushion
9.83 × 7.76 × 4.98
mm
G23001-9 4.81 ct Pear 15.01 × 8.00 × 5.97
mm
G23001-3 5.21 ct Pear 14.33 ×8.03
×6.69 mm
Crystals 2023, 13, x FOR PEER REVIEW 3 of 18
and so on [14]. Samples in this study are from gem dealers without specific origins, since
the origin is not an add-value parameter in the gem trade currently, while color comes
first when evaluating the chrysoberyl. The weight ranges from 1.97 to 7.43 carats, and the
details of all the samples can be found in Table 1.
Table 1. Basic information of the seventeen chrysoberyl samples investigated in this study.
No. Weight Shape Dimensions Sample Photo No. Weight Shape Dimensions Sample Photo
G23001-1 4.05 ct Triangular 9.15 × 9.23 × 6.57
mm
G23001-10 3.46 ct Pear 11.28 × 7.93 ×
5.80 mm
G23001-2 4.51 ct Pear 15.82 × 7.68 × 5.07
mm
G23001-11 2.79 ct Pear 10.74 × 7.71 ×
5.12 mm
G23001-3 5.21 ct Pear 14.33 × 8.03 × 6.69
mm
G23001-12 7.43 ct Pear 14.01 × 9.45 ×
8.09 mm
G23001-4 1.97 ct Pear 12.00 × 5.90 × 4.06
mm
G23001-13 2.09 ct Oval 8.96 × 6.91 × 4.65
mm
G23001-5 4.92 ct Pear 14.98 × 7.98 × 6.03
mm
G23001-14 2.12 ct Oval 8.94 × 6.95 × 4.73
mm
G23001-6 2.10 ct Pear 11.96 × 6.00 × 4.45
mm
G23001-15 6.00 ct Oval 10.75 × 9.84 ×
7.48 mm
G23001-7 2.87 ct Pear 13.76 × 6.82 × 4.33
mm
G23001-16 4.16 ct Oval 10.68 × 8.46 ×
6.34 mm
G23001-8 3.05 ct Pear 13.72 × 6.80 × 4.83
mm
G23001-17 3.09 ct Cushion
9.83 × 7.76 × 4.98
mm
G23001-9 4.81 ct Pear 15.01 × 8.00 × 5.97
mm
G23001-12 7.43 ct Pear 14.01 ×9.45
×8.09 mm
Crystals 2023, 13, x FOR PEER REVIEW 3 of 18
and so on [14]. Samples in this study are from gem dealers without specific origins, since
the origin is not an add-value parameter in the gem trade currently, while color comes
first when evaluating the chrysoberyl. The weight ranges from 1.97 to 7.43 carats, and the
details of all the samples can be found in Table 1.
Table 1. Basic information of the seventeen chrysoberyl samples investigated in this study.
No. Weight Shape Dimensions Sample Photo No. Weight Shape Dimensions Sample Photo
G23001-1 4.05 ct Triangular 9.15 × 9.23 × 6.57
mm
G23001-10 3.46 ct Pear 11.28 × 7.93 ×
5.80 mm
G23001-2 4.51 ct Pear 15.82 × 7.68 × 5.07
mm
G23001-11 2.79 ct Pear 10.74 × 7.71 ×
5.12 mm
G23001-3 5.21 ct Pear 14.33 × 8.03 × 6.69
mm
G23001-12 7.43 ct Pear 14.01 × 9.45 ×
8.09 mm
G23001-4 1.97 ct Pear 12.00 × 5.90 × 4.06
mm
G23001-13 2.09 ct Oval 8.96 × 6.91 × 4.65
mm
G23001-5 4.92 ct Pear 14.98 × 7.98 × 6.03
mm
G23001-14 2.12 ct Oval 8.94 × 6.95 × 4.73
mm
G23001-6 2.10 ct Pear 11.96 × 6.00 × 4.45
mm
G23001-15 6.00 ct Oval 10.75 × 9.84 ×
7.48 mm
G23001-7 2.87 ct Pear 13.76 × 6.82 × 4.33
mm
G23001-16 4.16 ct Oval 10.68 × 8.46 ×
6.34 mm
G23001-8 3.05 ct Pear 13.72 × 6.80 × 4.83
mm
G23001-17 3.09 ct Cushion
9.83 × 7.76 × 4.98
mm
G23001-9 4.81 ct Pear 15.01 × 8.00 × 5.97
mm
G23001-4 1.97 ct Pear 12.00 ×5.90
×4.06 mm
Crystals 2023, 13, x FOR PEER REVIEW 3 of 18
and so on [14]. Samples in this study are from gem dealers without specific origins, since
the origin is not an add-value parameter in the gem trade currently, while color comes
first when evaluating the chrysoberyl. The weight ranges from 1.97 to 7.43 carats, and the
details of all the samples can be found in Table 1.
Table 1. Basic information of the seventeen chrysoberyl samples investigated in this study.
No. Weight Shape Dimensions Sample Photo No. Weight Shape Dimensions Sample Photo
G23001-1 4.05 ct Triangular 9.15 × 9.23 × 6.57
mm
G23001-10 3.46 ct Pear 11.28 × 7.93 ×
5.80 mm
G23001-2 4.51 ct Pear 15.82 × 7.68 × 5.07
mm
G23001-11 2.79 ct Pear 10.74 × 7.71 ×
5.12 mm
G23001-3 5.21 ct Pear 14.33 × 8.03 × 6.69
mm
G23001-12 7.43 ct Pear 14.01 × 9.45 ×
8.09 mm
G23001-4 1.97 ct Pear 12.00 × 5.90 × 4.06
mm
G23001-13 2.09 ct Oval 8.96 × 6.91 × 4.65
mm
G23001-5 4.92 ct Pear 14.98 × 7.98 × 6.03
mm
G23001-14 2.12 ct Oval 8.94 × 6.95 × 4.73
mm
G23001-6 2.10 ct Pear 11.96 × 6.00 × 4.45
mm
G23001-15 6.00 ct Oval 10.75 × 9.84 ×
7.48 mm
G23001-7 2.87 ct Pear 13.76 × 6.82 × 4.33
mm
G23001-16 4.16 ct Oval 10.68 × 8.46 ×
6.34 mm
G23001-8 3.05 ct Pear 13.72 × 6.80 × 4.83
mm
G23001-17 3.09 ct Cushion
9.83 × 7.76 × 4.98
mm
G23001-9 4.81 ct Pear 15.01 × 8.00 × 5.97
mm
G23001-13 2.09 ct Oval 8.96 ×6.91
×4.65 mm
Crystals 2023, 13, x FOR PEER REVIEW 3 of 18
and so on [14]. Samples in this study are from gem dealers without specific origins, since
the origin is not an add-value parameter in the gem trade currently, while color comes
first when evaluating the chrysoberyl. The weight ranges from 1.97 to 7.43 carats, and the
details of all the samples can be found in Table 1.
Table 1. Basic information of the seventeen chrysoberyl samples investigated in this study.
No. Weight Shape Dimensions Sample Photo No. Weight Shape Dimensions Sample Photo
G23001-1 4.05 ct Triangular 9.15 × 9.23 × 6.57
mm
G23001-10 3.46 ct Pear 11.28 × 7.93 ×
5.80 mm
G23001-2 4.51 ct Pear 15.82 × 7.68 × 5.07
mm
G23001-11 2.79 ct Pear 10.74 × 7.71 ×
5.12 mm
G23001-3 5.21 ct Pear 14.33 × 8.03 × 6.69
mm
G23001-12 7.43 ct Pear 14.01 × 9.45 ×
8.09 mm
G23001-4 1.97 ct Pear 12.00 × 5.90 × 4.06
mm
G23001-13 2.09 ct Oval 8.96 × 6.91 × 4.65
mm
G23001-5 4.92 ct Pear 14.98 × 7.98 × 6.03
mm
G23001-14 2.12 ct Oval 8.94 × 6.95 × 4.73
mm
G23001-6 2.10 ct Pear 11.96 × 6.00 × 4.45
mm
G23001-15 6.00 ct Oval 10.75 × 9.84 ×
7.48 mm
G23001-7 2.87 ct Pear 13.76 × 6.82 × 4.33
mm
G23001-16 4.16 ct Oval 10.68 × 8.46 ×
6.34 mm
G23001-8 3.05 ct Pear 13.72 × 6.80 × 4.83
mm
G23001-17 3.09 ct Cushion
9.83 × 7.76 × 4.98
mm
G23001-9 4.81 ct Pear 15.01 × 8.00 × 5.97
mm
G23001-5 4.92 ct Pear 14.98 ×7.98
×6.03 mm
Crystals 2023, 13, x FOR PEER REVIEW 3 of 18
and so on [14]. Samples in this study are from gem dealers without specific origins, since
the origin is not an add-value parameter in the gem trade currently, while color comes
first when evaluating the chrysoberyl. The weight ranges from 1.97 to 7.43 carats, and the
details of all the samples can be found in Table 1.
Table 1. Basic information of the seventeen chrysoberyl samples investigated in this study.
No. Weight Shape Dimensions Sample Photo No. Weight Shape Dimensions Sample Photo
G23001-1 4.05 ct Triangular 9.15 × 9.23 × 6.57
mm
G23001-10 3.46 ct Pear 11.28 × 7.93 ×
5.80 mm
G23001-2 4.51 ct Pear 15.82 × 7.68 × 5.07
mm
G23001-11 2.79 ct Pear 10.74 × 7.71 ×
5.12 mm
G23001-3 5.21 ct Pear 14.33 × 8.03 × 6.69
mm
G23001-12 7.43 ct Pear 14.01 × 9.45 ×
8.09 mm
G23001-4 1.97 ct Pear 12.00 × 5.90 × 4.06
mm
G23001-13 2.09 ct Oval 8.96 × 6.91 × 4.65
mm
G23001-5 4.92 ct Pear 14.98 × 7.98 × 6.03
mm
G23001-14 2.12 ct Oval 8.94 × 6.95 × 4.73
mm
G23001-6 2.10 ct Pear 11.96 × 6.00 × 4.45
mm
G23001-15 6.00 ct Oval 10.75 × 9.84 ×
7.48 mm
G23001-7 2.87 ct Pear 13.76 × 6.82 × 4.33
mm
G23001-16 4.16 ct Oval 10.68 × 8.46 ×
6.34 mm
G23001-8 3.05 ct Pear 13.72 × 6.80 × 4.83
mm
G23001-17 3.09 ct Cushion
9.83 × 7.76 × 4.98
mm
G23001-9 4.81 ct Pear 15.01 × 8.00 × 5.97
mm
G23001-14 2.12 ct Oval 8.94 ×6.95
×4.73 mm
Crystals 2023, 13, x FOR PEER REVIEW 3 of 18
and so on [14]. Samples in this study are from gem dealers without specific origins, since
the origin is not an add-value parameter in the gem trade currently, while color comes
first when evaluating the chrysoberyl. The weight ranges from 1.97 to 7.43 carats, and the
details of all the samples can be found in Table 1.
Table 1. Basic information of the seventeen chrysoberyl samples investigated in this study.
No. Weight Shape Dimensions Sample Photo No. Weight Shape Dimensions Sample Photo
G23001-1 4.05 ct Triangular 9.15 × 9.23 × 6.57
mm
G23001-10 3.46 ct Pear 11.28 × 7.93 ×
5.80 mm
G23001-2 4.51 ct Pear 15.82 × 7.68 × 5.07
mm
G23001-11 2.79 ct Pear 10.74 × 7.71 ×
5.12 mm
G23001-3 5.21 ct Pear 14.33 × 8.03 × 6.69
mm
G23001-12 7.43 ct Pear 14.01 × 9.45 ×
8.09 mm
G23001-4 1.97 ct Pear 12.00 × 5.90 × 4.06
mm
G23001-13 2.09 ct Oval 8.96 × 6.91 × 4.65
mm
G23001-5 4.92 ct Pear 14.98 × 7.98 × 6.03
mm
G23001-14 2.12 ct Oval 8.94 × 6.95 × 4.73
mm
G23001-6 2.10 ct Pear 11.96 × 6.00 × 4.45
mm
G23001-15 6.00 ct Oval 10.75 × 9.84 ×
7.48 mm
G23001-7 2.87 ct Pear 13.76 × 6.82 × 4.33
mm
G23001-16 4.16 ct Oval 10.68 × 8.46 ×
6.34 mm
G23001-8 3.05 ct Pear 13.72 × 6.80 × 4.83
mm
G23001-17 3.09 ct Cushion
9.83 × 7.76 × 4.98
mm
G23001-9 4.81 ct Pear 15.01 × 8.00 × 5.97
mm
G23001-6 2.10 ct Pear 11.96 ×6.00
×4.45 mm
Crystals 2023, 13, x FOR PEER REVIEW 3 of 18
and so on [14]. Samples in this study are from gem dealers without specific origins, since
the origin is not an add-value parameter in the gem trade currently, while color comes
first when evaluating the chrysoberyl. The weight ranges from 1.97 to 7.43 carats, and the
details of all the samples can be found in Table 1.
Table 1. Basic information of the seventeen chrysoberyl samples investigated in this study.
No. Weight Shape Dimensions Sample Photo No. Weight Shape Dimensions Sample Photo
G23001-1 4.05 ct Triangular 9.15 × 9.23 × 6.57
mm
G23001-10 3.46 ct Pear 11.28 × 7.93 ×
5.80 mm
G23001-2 4.51 ct Pear 15.82 × 7.68 × 5.07
mm
G23001-11 2.79 ct Pear 10.74 × 7.71 ×
5.12 mm
G23001-3 5.21 ct Pear 14.33 × 8.03 × 6.69
mm
G23001-12 7.43 ct Pear 14.01 × 9.45 ×
8.09 mm
G23001-4 1.97 ct Pear 12.00 × 5.90 × 4.06
mm
G23001-13 2.09 ct Oval 8.96 × 6.91 × 4.65
mm
G23001-5 4.92 ct Pear 14.98 × 7.98 × 6.03
mm
G23001-14 2.12 ct Oval 8.94 × 6.95 × 4.73
mm
G23001-6 2.10 ct Pear 11.96 × 6.00 × 4.45
mm
G23001-15 6.00 ct Oval 10.75 × 9.84 ×
7.48 mm
G23001-7 2.87 ct Pear 13.76 × 6.82 × 4.33
mm
G23001-16 4.16 ct Oval 10.68 × 8.46 ×
6.34 mm
G23001-8 3.05 ct Pear 13.72 × 6.80 × 4.83
mm
G23001-17 3.09 ct Cushion
9.83 × 7.76 × 4.98
mm
G23001-9 4.81 ct Pear 15.01 × 8.00 × 5.97
mm
G23001-15 6.00 ct Oval 10.75 ×9.84
×7.48 mm
Crystals 2023, 13, x FOR PEER REVIEW 3 of 18
and so on [14]. Samples in this study are from gem dealers without specific origins, since
the origin is not an add-value parameter in the gem trade currently, while color comes
first when evaluating the chrysoberyl. The weight ranges from 1.97 to 7.43 carats, and the
details of all the samples can be found in Table 1.
Table 1. Basic information of the seventeen chrysoberyl samples investigated in this study.
No. Weight Shape Dimensions Sample Photo No. Weight Shape Dimensions Sample Photo
G23001-1 4.05 ct Triangular 9.15 × 9.23 × 6.57
mm
G23001-10 3.46 ct Pear 11.28 × 7.93 ×
5.80 mm
G23001-2 4.51 ct Pear 15.82 × 7.68 × 5.07
mm
G23001-11 2.79 ct Pear 10.74 × 7.71 ×
5.12 mm
G23001-3 5.21 ct Pear 14.33 × 8.03 × 6.69
mm
G23001-12 7.43 ct Pear 14.01 × 9.45 ×
8.09 mm
G23001-4 1.97 ct Pear 12.00 × 5.90 × 4.06
mm
G23001-13 2.09 ct Oval 8.96 × 6.91 × 4.65
mm
G23001-5 4.92 ct Pear 14.98 × 7.98 × 6.03
mm
G23001-14 2.12 ct Oval 8.94 × 6.95 × 4.73
mm
G23001-6 2.10 ct Pear 11.96 × 6.00 × 4.45
mm
G23001-15 6.00 ct Oval 10.75 × 9.84 ×
7.48 mm
G23001-7 2.87 ct Pear 13.76 × 6.82 × 4.33
mm
G23001-16 4.16 ct Oval 10.68 × 8.46 ×
6.34 mm
G23001-8 3.05 ct Pear 13.72 × 6.80 × 4.83
mm
G23001-17 3.09 ct Cushion
9.83 × 7.76 × 4.98
mm
G23001-9 4.81 ct Pear 15.01 × 8.00 × 5.97
mm
G23001-7 2.87 ct Pear 13.76 ×6.82
×4.33 mm
Crystals 2023, 13, x FOR PEER REVIEW 3 of 18
and so on [14]. Samples in this study are from gem dealers without specific origins, since
the origin is not an add-value parameter in the gem trade currently, while color comes
first when evaluating the chrysoberyl. The weight ranges from 1.97 to 7.43 carats, and the
details of all the samples can be found in Table 1.
Table 1. Basic information of the seventeen chrysoberyl samples investigated in this study.
No. Weight Shape Dimensions Sample Photo No. Weight Shape Dimensions Sample Photo
G23001-1 4.05 ct Triangular 9.15 × 9.23 × 6.57
mm
G23001-10 3.46 ct Pear 11.28 × 7.93 ×
5.80 mm
G23001-2 4.51 ct Pear 15.82 × 7.68 × 5.07
mm
G23001-11 2.79 ct Pear 10.74 × 7.71 ×
5.12 mm
G23001-3 5.21 ct Pear 14.33 × 8.03 × 6.69
mm
G23001-12 7.43 ct Pear 14.01 × 9.45 ×
8.09 mm
G23001-4 1.97 ct Pear 12.00 × 5.90 × 4.06
mm
G23001-13 2.09 ct Oval 8.96 × 6.91 × 4.65
mm
G23001-5 4.92 ct Pear 14.98 × 7.98 × 6.03
mm
G23001-14 2.12 ct Oval 8.94 × 6.95 × 4.73
mm
G23001-6 2.10 ct Pear 11.96 × 6.00 × 4.45
mm
G23001-15 6.00 ct Oval 10.75 × 9.84 ×
7.48 mm
G23001-7 2.87 ct Pear 13.76 × 6.82 × 4.33
mm
G23001-16 4.16 ct Oval 10.68 × 8.46 ×
6.34 mm
G23001-8 3.05 ct Pear 13.72 × 6.80 × 4.83
mm
G23001-17 3.09 ct Cushion
9.83 × 7.76 × 4.98
mm
G23001-9 4.81 ct Pear 15.01 × 8.00 × 5.97
mm
G23001-16 4.16 ct Oval 10.68 ×8.46
×6.34 mm
Crystals 2023, 13, x FOR PEER REVIEW 3 of 18
and so on [14]. Samples in this study are from gem dealers without specific origins, since
the origin is not an add-value parameter in the gem trade currently, while color comes
first when evaluating the chrysoberyl. The weight ranges from 1.97 to 7.43 carats, and the
details of all the samples can be found in Table 1.
Table 1. Basic information of the seventeen chrysoberyl samples investigated in this study.
No. Weight Shape Dimensions Sample Photo No. Weight Shape Dimensions Sample Photo
G23001-1 4.05 ct Triangular 9.15 × 9.23 × 6.57
mm
G23001-10 3.46 ct Pear 11.28 × 7.93 ×
5.80 mm
G23001-2 4.51 ct Pear 15.82 × 7.68 × 5.07
mm
G23001-11 2.79 ct Pear 10.74 × 7.71 ×
5.12 mm
G23001-3 5.21 ct Pear 14.33 × 8.03 × 6.69
mm
G23001-12 7.43 ct Pear 14.01 × 9.45 ×
8.09 mm
G23001-4 1.97 ct Pear 12.00 × 5.90 × 4.06
mm
G23001-13 2.09 ct Oval 8.96 × 6.91 × 4.65
mm
G23001-5 4.92 ct Pear 14.98 × 7.98 × 6.03
mm
G23001-14 2.12 ct Oval 8.94 × 6.95 × 4.73
mm
G23001-6 2.10 ct Pear 11.96 × 6.00 × 4.45
mm
G23001-15 6.00 ct Oval 10.75 × 9.84 ×
7.48 mm
G23001-7 2.87 ct Pear 13.76 × 6.82 × 4.33
mm
G23001-16 4.16 ct Oval 10.68 × 8.46 ×
6.34 mm
G23001-8 3.05 ct Pear 13.72 × 6.80 × 4.83
mm
G23001-17 3.09 ct Cushion
9.83 × 7.76 × 4.98
mm
G23001-9 4.81 ct Pear 15.01 × 8.00 × 5.97
mm
G23001-8 3.05 ct Pear 13.72 ×6.80
×4.83 mm
Crystals 2023, 13, x FOR PEER REVIEW 3 of 18
and so on [14]. Samples in this study are from gem dealers without specific origins, since
the origin is not an add-value parameter in the gem trade currently, while color comes
first when evaluating the chrysoberyl. The weight ranges from 1.97 to 7.43 carats, and the
details of all the samples can be found in Table 1.
Table 1. Basic information of the seventeen chrysoberyl samples investigated in this study.
No. Weight Shape Dimensions Sample Photo No. Weight Shape Dimensions Sample Photo
G23001-1 4.05 ct Triangular 9.15 × 9.23 × 6.57
mm
G23001-10 3.46 ct Pear 11.28 × 7.93 ×
5.80 mm
G23001-2 4.51 ct Pear 15.82 × 7.68 × 5.07
mm
G23001-11 2.79 ct Pear 10.74 × 7.71 ×
5.12 mm
G23001-3 5.21 ct Pear 14.33 × 8.03 × 6.69
mm
G23001-12 7.43 ct Pear 14.01 × 9.45 ×
8.09 mm
G23001-4 1.97 ct Pear 12.00 × 5.90 × 4.06
mm
G23001-13 2.09 ct Oval 8.96 × 6.91 × 4.65
mm
G23001-5 4.92 ct Pear 14.98 × 7.98 × 6.03
mm
G23001-14 2.12 ct Oval 8.94 × 6.95 × 4.73
mm
G23001-6 2.10 ct Pear 11.96 × 6.00 × 4.45
mm
G23001-15 6.00 ct Oval 10.75 × 9.84 ×
7.48 mm
G23001-7 2.87 ct Pear 13.76 × 6.82 × 4.33
mm
G23001-16 4.16 ct Oval 10.68 × 8.46 ×
6.34 mm
G23001-8 3.05 ct Pear 13.72 × 6.80 × 4.83
mm
G23001-17 3.09 ct Cushion
9.83 × 7.76 × 4.98
mm
G23001-9 4.81 ct Pear 15.01 × 8.00 × 5.97
mm
G23001-17 3.09 ct Cushion 9.83 ×7.76
×4.98 mm
Crystals 2023, 13, x FOR PEER REVIEW 3 of 18
and so on [14]. Samples in this study are from gem dealers without specific origins, since
the origin is not an add-value parameter in the gem trade currently, while color comes
first when evaluating the chrysoberyl. The weight ranges from 1.97 to 7.43 carats, and the
details of all the samples can be found in Table 1.
Table 1. Basic information of the seventeen chrysoberyl samples investigated in this study.
No. Weight Shape Dimensions Sample Photo No. Weight Shape Dimensions Sample Photo
G23001-1 4.05 ct Triangular 9.15 × 9.23 × 6.57
mm
G23001-10 3.46 ct Pear 11.28 × 7.93 ×
5.80 mm
G23001-2 4.51 ct Pear 15.82 × 7.68 × 5.07
mm
G23001-11 2.79 ct Pear 10.74 × 7.71 ×
5.12 mm
G23001-3 5.21 ct Pear 14.33 × 8.03 × 6.69
mm
G23001-12 7.43 ct Pear 14.01 × 9.45 ×
8.09 mm
G23001-4 1.97 ct Pear 12.00 × 5.90 × 4.06
mm
G23001-13 2.09 ct Oval 8.96 × 6.91 × 4.65
mm
G23001-5 4.92 ct Pear 14.98 × 7.98 × 6.03
mm
G23001-14 2.12 ct Oval 8.94 × 6.95 × 4.73
mm
G23001-6 2.10 ct Pear 11.96 × 6.00 × 4.45
mm
G23001-15 6.00 ct Oval 10.75 × 9.84 ×
7.48 mm
G23001-7 2.87 ct Pear 13.76 × 6.82 × 4.33
mm
G23001-16 4.16 ct Oval 10.68 × 8.46 ×
6.34 mm
G23001-8 3.05 ct Pear 13.72 × 6.80 × 4.83
mm
G23001-17 3.09 ct Cushion
9.83 × 7.76 × 4.98
mm
G23001-9 4.81 ct Pear 15.01 × 8.00 × 5.97
mm
G23001-9 4.81 ct Pear 15.01 ×8.00
×5.97 mm
Crystals 2023, 13, x FOR PEER REVIEW 3 of 18
and so on [14]. Samples in this study are from gem dealers without specific origins, since
the origin is not an add-value parameter in the gem trade currently, while color comes
first when evaluating the chrysoberyl. The weight ranges from 1.97 to 7.43 carats, and the
details of all the samples can be found in Table 1.
Table 1. Basic information of the seventeen chrysoberyl samples investigated in this study.
No. Weight Shape Dimensions Sample Photo No. Weight Shape Dimensions Sample Photo
G23001-1 4.05 ct Triangular 9.15 × 9.23 × 6.57
mm
G23001-10 3.46 ct Pear 11.28 × 7.93 ×
5.80 mm
G23001-2 4.51 ct Pear 15.82 × 7.68 × 5.07
mm
G23001-11 2.79 ct Pear 10.74 × 7.71 ×
5.12 mm
G23001-3 5.21 ct Pear 14.33 × 8.03 × 6.69
mm
G23001-12 7.43 ct Pear 14.01 × 9.45 ×
8.09 mm
G23001-4 1.97 ct Pear 12.00 × 5.90 × 4.06
mm
G23001-13 2.09 ct Oval 8.96 × 6.91 × 4.65
mm
G23001-5 4.92 ct Pear 14.98 × 7.98 × 6.03
mm
G23001-14 2.12 ct Oval 8.94 × 6.95 × 4.73
mm
G23001-6 2.10 ct Pear 11.96 × 6.00 × 4.45
mm
G23001-15 6.00 ct Oval 10.75 × 9.84 ×
7.48 mm
G23001-7 2.87 ct Pear 13.76 × 6.82 × 4.33
mm
G23001-16 4.16 ct Oval 10.68 × 8.46 ×
6.34 mm
G23001-8 3.05 ct Pear 13.72 × 6.80 × 4.83
mm
G23001-17 3.09 ct Cushion
9.83 × 7.76 × 4.98
mm
G23001-9 4.81 ct Pear 15.01 × 8.00 × 5.97
mm
The internal inclusion features were observed under a gemological microscope of
magnification up to 80
×
, equipped with various lighting conditions. A Cannon 500D
(Kanagawa, Japan) camera was applied to capture the internal features of the chrysoberyl
in this article.
All samples were identified using Fourier transform infrared (FTIR) spectroscopy on a
TENSOR II FTIR spectrometer (Karlsruhe, Germany) furnished with a KBr beam splitter
and RT-DLaTGS detector. The spectra were collected between 2000 and 4000 cm
−1
using
eight scans at 7.5 kHz and a spectral resolution of 4 cm
−1
. In total, 17 transmission spectra
were recorded.
The Horiba Xplora Plus Raman system (Kyoto, Japan) was used to perform micro-
Raman spectroscopy on chrysoberyl samples to detect mineral inclusions. The instrument
had three distinct lasers with varying wavelengths, including 473 nm, 532 nm, and 783 nm.
In this study, each laser was administered to chrysoberyl samples using 100% power
energy to investigate their reactivity to different lasers. The spectra were obtained in the
100–2000 cm−1
area with a scanning period of 15 s and 10 scan accumulations. All of the
spectra were compared to the RRUFF database (https://rruff.info, accessed on 1 April

Crystals 2023,13, 1580 4 of 17
2023), and the minerals were recognized as such [
15
]. Thermal damage to the examined
sites was not found during host or inclusion Raman testing under 50-times objective.
Meanwhile, the P.L. spectrum was also collected using the 473 nm laser. The photo-
luminescence (P.L.) spectroscopy was likewise acquired utilizing the three lasers on the
Horiba Xplora Plus Raman system. The P.L. spectra were taken in the 500–750 nm band
over a 15 s scanning period with 10 scan accumulations.
UV-Vis absorption spectra were recorded using a Gem3000 Ultraviolet-visible (UV-Vis)
spectrophotometer (Dongguan, China) in the 200–1000 nm range. Furthermore, the CIE
testing was also performed on this machine to obtain the LAB parameters to decode the
color variation of the samples and the pattern behind them in this study.
The SYNTHdetect instrument (London, UK) was used to study the luminescence
properties of the sample studied, which was originally designed to observe the lumines-
cence behavior of diamonds. The results show that luminescence is a very useful tool for
studying diamonds, particularly for distinguishing lab-grown diamonds from their natural
counterparts, as previously reported by McGuiness et al. [
16
]. Time-gated luminescence
imaging technology, which has been employed for diamond identification and colorless
cubic zirconia [
17
–
19
], was the essential principle applied to equipment. Unlike the typical
U.V. light box used in gemology, which has a 254 nm shortwave and a 365 nm longwave,
the SYNTHdetect has a U.V. light with a wavelength of less than 220 nm, allowing it to
activate diverse luminescent phenomena. Generally, we applied the methods mentioned
above to explore the spectral, gemological, and chemical features of the canary yellow
chrysoberyl in this study.
The chemical composition analyses were performed with a Spectro Midex type energy
dispersive X-ray fluorescence (EDXRF) (Kleve, Germany) equipped with calculating soft-
ware X-LabPro 5.1R215(6), using a Ta target with the spot size of 2 mm. The machine was
calibrated by MCA (Multi-Channel Analysis) with a reference material supplied by the
equipment supplier.
3. Results
3.1. Gemological Results
Generally, samples show an attractive color, with yellow as the primary hue, accompa-
nied by a greenish secondary hue. The saturation varies from low to medium while the
tone is bright. The medium to high clarity and the high transparency qualify the samples
as gem-quality. Even though various inclusions were observed under the microscope, no
distinct fluorescents were observed when exposed to 365 nm and 254 nm; however, the
220 nm excited green fluorescence of weak to medium strength. All gemological features
are summarized in Table 2.
Table 2. Gemological properties of chrysoberyl samples in this study.
Weight 1.97 ct to 7.43 ct
Color Yellow is the primary hue, accompanied by a tint of greenish
secondary hue, with low to medium saturation
Clarity Medium to high clarity
Refractive index 1.743–1.751, birefringence: 0.008
Optical character Biaxial positive
Fluorescence Inert under 365 nm, exhibiting green fluorescence of various
strengths under the 220 nm
Internal features
1. Fluids
2. Straight growth lines
3. Minerals inclusions, muscovite, sillimanite, and quartz
4. Carbon-related substances, CO2, carbon, and calcite
Chemical features Rich in Fe, a trace of V and Cr, Sn of various levels

Crystals 2023,13, 1580 5 of 17
3.2. Observation of Inclusions and Raman Results
The chrysoberyl samples investigated in this study appear to be very rich in inclusions.
The typically encountered inclusions can be summarized as growth lines, fluids, carbon,
and mineral crystals; each category will be described separately.
Growth Lines
As shown in Figure 2, the chrysoberyl samples possess abundant growth lines within
their gem host, most of which are straight and condensed lines, while the curved rolling
lines can also be occasionally observed in one sample. The straight lines exist in three
ways. Firstly, they can be filled with short needle-like inclusions oriented in the same
direction. Secondly, it appears to be purely long, condensed, and has parallel growth lines;
additionally, milky, and cloudy textures show along with the growth lines, which can be
the main contributor to the cat’s eye effect. However, no distinct chatoyance effect was
observed, mainly due to the area of the milky and cloudy texture being too small to make
an obvious influence on the gem host. But it is important to point out that the common
chrysoberyl and cat’s eye chrysoberyl are the same material that can occur in the same
rough. At the same time, whether the finished stone is classified as common chrysoberyl or
cat’s eye depends on the cutting and fashion planning.
Crystals 2023, 13, x FOR PEER REVIEW 6 of 18
3.2. Observation of Inclusions and Raman Results
The chrysoberyl samples investigated in this study appear to be very rich in inclu-
sions. The typically encountered inclusions can be summarized as growth lines, fluids,
carbon, and mineral crystals; each category will be described separately.
Growth Lines
As shown in Figure 2, the chrysoberyl samples possess abundant growth lines within
their gem host, most of which are straight and condensed lines, while the curved rolling
lines can also be occasionally observed in one sample. The straight lines exist in three
ways. Firstly, they can be filled with short needle-like inclusions oriented in the same di-
rection. Secondly, it appears to be purely long, condensed, and has parallel growth lines;
additionally, milky, and cloudy textures show along with the growth lines, which can be
the main contributor to the cat’s eye effect. However, no distinct chatoyance effect was
observed, mainly due to the area of the milky and cloudy texture being too small to make
an obvious influence on the gem host. But it is important to point out that the common
chrysoberyl and cat’s eye chrysoberyl are the same material that can occur in the same
rough. At the same time, whether the finished stone is classified as common chrysoberyl
or cat’s eye depends on the cuing and fashion planning.
Furthermore, a V-shape paern consisting of two sets of straight growth lines in two
directions is commonly encountered in the samples studied. The V-shape growth line
originates from the cyclical twins due to the repeated twining on the {031} plane of the
chrysoberyl, consistent with a previous study on chrysoberyl from the New England
Placer Deposits, New South Wales, Australia [14]. Meanwhile, a step-like paern was also
seen in one sample, suggesting a growth mechanism.
Figure 2. The typical growth lines encountered in the samples studied. (a): Needle-like inclusions
arranged long the grow lines; (b,c): straight lines, with the laer being held by the milky and cloudy
texture; (d): V-shape paern due to the cyclical twins; (e): step-like paern; (f): curved and rolling
paern.
Figure 2.
The typical growth lines encountered in the samples studied. (
a
): Needle-like inclusions
arranged long the grow lines; (
b
,
c
): straight lines, with the latter being held by the milky and
cloudy texture; (
d
): V-shape pattern due to the cyclical twins; (
e
): step-like pattern; (
f
): curved and
rolling pattern.
Furthermore, a V-shape pattern consisting of two sets of straight growth lines in two
directions is commonly encountered in the samples studied. The V-shape growth line
originates from the cyclical twins due to the repeated twining on the {031} plane of the
chrysoberyl, consistent with a previous study on chrysoberyl from the New England Placer
Deposits, New South Wales, Australia [
14
]. Meanwhile, a step-like pattern was also seen in
one sample, suggesting a growth mechanism.

Crystals 2023,13, 1580 6 of 17
3.3. Fluids
Fluid inclusions are distributed in almost all the samples. The fluid is usually arranged
along certain healed fissures, as demonstrated in Figure 3d. A higher magnification may
reveal that the fluid is filling the irregular cavity in Figure 3b. Further Raman testing reveals
the fluids mainly consist of CO
2
, showing the feature peaks at 1282 and 1386 cm
−1
, as
shown in Figure 4.
Crystals 2023, 13, x FOR PEER REVIEW 7 of 18
3.3. Fluids
Fluid inclusions are distributed in almost all the samples. The fluid is usually ar-
ranged along certain healed fissures, as demonstrated in Figure 3d. A higher magnifica-
tion may reveal that the fluid is filling the irregular cavity in Figure 3b. Further Raman
testing reveals the fluids mainly consist of CO2, showing the feature peaks at 1282 and
1386 cm−1, as shown in Figure 4.
Figure 3. Fluid inclusions were observed in most of the samples. Some fluid inclusions appeared
irregularly (a–c), while others resembled fingerprints (d).
Figure 4. Raman spectra of calcite crystals, amorphous carbon and CO2. Peaks in the inclusion
spectra that are marked with an asterisk * are from the host chrysoberyl.
3.4. Sillimanite Needles
Many long needles are distributed in the samples, and unlike the short needles within
the growth lines, these needles are somehow curved and much longer, up to 1–2 mm.
They are arranged randomly and show good transparency. As shown in Figure 5, some
Figure 3.
Fluid inclusions were observed in most of the samples. Some fluid inclusions appeared
irregularly (a–c), while others resembled fingerprints (d).
Crystals 2023, 13, x FOR PEER REVIEW 7 of 18
3.3. Fluids
Fluid inclusions are distributed in almost all the samples. The fluid is usually ar-
ranged along certain healed fissures, as demonstrated in Figure 3d. A higher magnifica-
tion may reveal that the fluid is filling the irregular cavity in Figure 3b. Further Raman
testing reveals the fluids mainly consist of CO2, showing the feature peaks at 1282 and
1386 cm−1, as shown in Figure 4.
Figure 3. Fluid inclusions were observed in most of the samples. Some fluid inclusions appeared
irregularly (a–c), while others resembled fingerprints (d).
Figure 4. Raman spectra of calcite crystals, amorphous carbon and CO2. Peaks in the inclusion
spectra that are marked with an asterisk * are from the host chrysoberyl.
3.4. Sillimanite Needles
Many long needles are distributed in the samples, and unlike the short needles within
the growth lines, these needles are somehow curved and much longer, up to 1–2 mm.
They are arranged randomly and show good transparency. As shown in Figure 5, some
Figure 4.
Raman spectra of calcite crystals, amorphous carbon and CO
2
. Peaks in the inclusion
spectra that are marked with an asterisk * are from the host chrysoberyl.
3.4. Sillimanite Needles
Many long needles are distributed in the samples, and unlike the short needles within
the growth lines, these needles are somehow curved and much longer, up to 1–2 mm. They
are arranged randomly and show good transparency. As shown in Figure 5, some needles
are partially altered by external substances such as iron, showing distinct yellowish and

Crystals 2023,13, 1580 7 of 17
brownish hues, contrasting with the colorless host. The Raman spectrum identifies these
needles as sillimanite, with feature peaks at 141, 235, 308, 456,590, and 705 cm
−1
, consistent
with those from RRUFF, an online spectrum database (Figure 6).
Crystals 2023, 13, x FOR PEER REVIEW 8 of 18
needles are partially altered by external substances such as iron, showing distinct yellow-
ish and brownish hues, contrasting with the colorless host. The Raman spectrum identifies
these needles as sillimanite, with feature peaks at 141, 235, 308, 456,590, and 705 cm−1,
consistent with those from RRUFF, an online spectrum database (Figure 6).
Figure 5. Long and transparent sillimanite needles are scaered in the gem host, some of which are
somehow partially altered by external substances.
Figure 6. Raman spectra of sillimanite, quar, and muscovite inclusions within the chrysoberyl host.
Peaks in the inclusion spectra that are marked with an asterisk * are from the host chrys-
oberyl.
3.5. Quar and Muscovite
Quar occurs as an irregular and colorless grain within the chrysoberyl host without
any intrinsically crystalline structure. All the quar grains detected were distributed
along the healed fractures, accompanied by mica and fluids, as shown in Figure 7. Such
an association may imply the geological origin of the gem host, which will be discussed
in the discussion part, along with the chemical data. The Raman spectrum identified the
quar crystal with typical peaks at 126, 200, 461, and 929 cm−1, consistent with those from
RRUFF (Figure 6).
Figure 5.
Long and transparent sillimanite needles are scattered in the gem host, some of which are
somehow partially altered by external substances.
Crystals 2023, 13, x FOR PEER REVIEW 8 of 18
needles are partially altered by external substances such as iron, showing distinct yellow-
ish and brownish hues, contrasting with the colorless host. The Raman spectrum identifies
these needles as sillimanite, with feature peaks at 141, 235, 308, 456,590, and 705 cm−1,
consistent with those from RRUFF, an online spectrum database (Figure 6).
Figure 5. Long and transparent sillimanite needles are scaered in the gem host, some of which are
somehow partially altered by external substances.
Figure 6. Raman spectra of sillimanite, quar, and muscovite inclusions within the chrysoberyl host.
Peaks in the inclusion spectra that are marked with an asterisk * are from the host chrys-
oberyl.
3.5. Quar and Muscovite
Quar occurs as an irregular and colorless grain within the chrysoberyl host without
any intrinsically crystalline structure. All the quar grains detected were distributed
along the healed fractures, accompanied by mica and fluids, as shown in Figure 7. Such
an association may imply the geological origin of the gem host, which will be discussed
in the discussion part, along with the chemical data. The Raman spectrum identified the
quar crystal with typical peaks at 126, 200, 461, and 929 cm−1, consistent with those from
RRUFF (Figure 6).
Figure 6.
Raman spectra of sillimanite, quartz, and muscovite inclusions within the chrysoberyl host.
Peaks in the inclusion spectra that are marked with an asterisk * are from the host chrysoberyl.
3.5. Quartz and Muscovite
Quartz occurs as an irregular and colorless grain within the chrysoberyl host without
any intrinsically crystalline structure. All the quartz grains detected were distributed along
the healed fractures, accompanied by mica and fluids, as shown in Figure 7. Such an
association may imply the geological origin of the gem host, which will be discussed in the
discussion part, along with the chemical data. The Raman spectrum identified the quartz
crystal with typical peaks at 126, 200, 461, and 929 cm
−1
, consistent with those from RRUFF
(Figure 6).
Mica grains are also frequently encountered in these samples, usually coming as
anhedral and transparent. The mica is also identified as a muscovite variety by the Raman
spectrum with reference from the RRUFF online data.
Calcite is one of the most abundant carbonate minerals, which can be found in the
ruby from marble-hosted sources, such as Mogok in Burma and Vietnam. Calcite can
be used as indicator to distinguish ruby marble hosted (Burman and Vietnam) from the
amphibole hosted, mostly in Mozambique and Madagascar. As shown in Figure 7, the
calcite inclusions are found as anhedral colorless and transparent crystals, some of which
may show rhombohedral morphology owing to their crystallinity. The Raman spectrum

Crystals 2023,13, 1580 8 of 17
results agree with the standard calcite features from RRUFF, with a prominent band at
1082 cm−1and bands at 181, 280, 775, and 929 cm−1(Figure 4).
Crystals 2023, 13, x FOR PEER REVIEW 9 of 18
Figure 7. Several solid inclusions were found in the samples studied, including irregular calcite (a),
muscovite(b,d), quar (c), sillimanite (e), and carbon(f).
Mica grains are also frequently encountered in these samples, usually coming as an-
hedral and transparent. The mica is also identified as a muscovite variety by the Raman
spectrum with reference from the RRUFF online data.
Calcite is one of the most abundant carbonate minerals, which can be found in the
ruby from marble-hosted sources, such as Mogok in Burma and Vietnam. Calcite can be
used as indicator to distinguish ruby marble hosted (Burman and Vietnam) from the am-
phibole hosted, mostly in Mozambique and Madagascar. As shown in Figure 7, the calcite
inclusions are found as anhedral colorless and transparent crystals, some of which may
show rhombohedral morphology owing to their crystallinity. The Raman spectrum re-
sults agree with the standard calcite features from RRUFF, with a prominent band at 1082
cm−1 and bands at 181, 280, 775, and 929 cm−1 (Figure 4).
One opaque plate was observed along the girdle of one sample (Figure 7), exhibiting
metallic luster, which shows a prominent band centered at 1583 cm−1, possibly indicating
a carbon-related material, graphite, as shown in Figure 4. Graphite has been reported in
many gemstones, such as sapphire, ruby, and spinel. Since chrysoberyl is an oxide mineral
usually occurring with corundum and spinel, it is reasonable to find graphite in chryso-
beryl. Furthermore, recent studies present that graphite can be used as one geothermom-
eter to estimate the temperature and pressure during the formation of the gem host [20].
3.6. Raman Spectrum on the Chrysoberyl Host
Moreover, we have applied three different lasers to the chrysoberyl host in this study
to explore their spectral features, including 473, 532, and 785 nm. The typical spectrum is
reported in Figure 8. All the samples are not oriented along their optical axis; thus, the
spectrum should be classified as unoriented. In general, the 930 cm−1 peak appears at all
three lasers as the strongest, while the 636 cm−1 peak appears weak in the 785 nm and
strong enough to be a primary peak in the 532 and 473 nm lasers. By comparison, the 239
and 707 cm−1 can only be seen with the 785 nm laser. Accompanied by a series peak in the
300–600 cm−1 range, the 346 peak is prominent in the 785 nm, which is very weak in the
Figure 7.
Several solid inclusions were found in the samples studied, including irregular calcite (
a
),
muscovite (b,d), quartz (c), sillimanite (e), and carbon (f).
One opaque plate was observed along the girdle of one sample (Figure 7), exhibiting
metallic luster, which shows a prominent band centered at 1583 cm
−1
, possibly indicating
a carbon-related material, graphite, as shown in Figure 4. Graphite has been reported in
many gemstones, such as sapphire, ruby, and spinel. Since chrysoberyl is an oxide mineral
usually occurring with corundum and spinel, it is reasonable to find graphite in chrysoberyl.
Furthermore, recent studies present that graphite can be used as one geothermometer to
estimate the temperature and pressure during the formation of the gem host [20].
3.6. Raman Spectrum on the Chrysoberyl Host
Moreover, we have applied three different lasers to the chrysoberyl host in this study
to explore their spectral features, including 473, 532, and 785 nm. The typical spectrum
is reported in Figure 8. All the samples are not oriented along their optical axis; thus, the
spectrum should be classified as unoriented. In general, the 930 cm
−1
peak appears at all
three lasers as the strongest, while the 636 cm
−1
peak appears weak in the 785 nm and
strong enough to be a primary peak in the 532 and 473 nm lasers. By comparison, the 239
and 707 cm
−1
can only be seen with the 785 nm laser. Accompanied by a series peak in the
300–600 cm
−1
range, the 346 peak is prominent in the 785 nm, which is very weak in the
532 nm and nearly none in the 473 nm laser. The 930 cm
−1
peaks can be excited by all three
lasers, and such a feature agrees with a recent study [21].
This comparison study with three different lasers may help provide a quick guide
when using the Raman spectrum to identify the gemstone. The typical feature peak can
be a good indicator to tell the results instead of checking the spectrum among the Raman
database with thousands of unrelated peaks, giving high efficiency. This result is especially
helpful when detecting the chrysoberyl inclusions in other gems; the 930 cm
−1
peak can be a
very useful key to lead the way to identify the chrysoberyl since most of the mineral Raman

Crystals 2023,13, 1580 9 of 17
spectra are not as clear as the host, and they are usually masked by the host spectrally
when the host is strongly fluorescent. And even if the host is inert to the laser, the depth of
the inclusion may prohibit a decent view of the inclusion.
Crystals 2023, 13, x FOR PEER REVIEW 10 of 18
532 nm and nearly none in the 473 nm laser. The 930 cm−1 peaks can be excited by all three
lasers, and such a feature agrees with a recent study [21].
Figure 8. Raman spectra of the chrysoberyl host tested by three different lasers, 473, 532, and 785
nm.
This comparison study with three different lasers may help provide a quick guide
when using the Raman spectrum to identify the gemstone. The typical feature peak can
be a good indicator to tell the results instead of checking the spectrum among the Raman
database with thousands of unrelated peaks, giving high efficiency. This result is espe-
cially helpful when detecting the chrysoberyl inclusions in other gems; the 930 cm−1 peak
can be a very useful key to lead the way to identify the chrysoberyl since most of the min-
eral Raman spectra are not as clear as the host, and they are usually masked by the host
spectrally when the host is strongly fluorescent. And even if the host is inert to the laser,
the depth of the inclusion may prohibit a decent view of the inclusion.
3.7. FTIR Spectrum
Each sample was subjected to the FTIR transmission spectrum test, and 17 spectra
were recorded, among which the three representative spectra were displayed in Figure 9.
The FTIR features can be described as follows:
(1) In the 2000–2500 cm−1 range, two distinct peaks at 2405 and 2160 cm−1 are present
in all samples, which can prove the samples as natural, differentiating them from the syn-
thetic counterparts; as a maer of fact, such a paern was absent in the synthetic chryso-
beryl, as reported in the previous studies [22–26].
(2) In the 2500–3000 cm−1 range, several weak shoulders are observed at 2762, 2840,
and 2920, which could also be present in the synthetic material. Water and/or hydroxyl
absorption bands in the 2500 to 3000 cm−1 range may come from the hydrous inclu-
sions.
(3) In the range between 3000 and 3500 cm−1, the 3223 peak is present in all samples,
which can be accompanied by the 3112 shoulders of various strengths and the 3301 cm−1,
along with the 3412 and 3432 cm−1 peaks.
Although chrysoberyl is well known in the gemological fields, the transmission FTIR
spectrum is not sufficiently studied as those of corundum, which is also an oxide mineral,
and the gem varieties ruby and sapphire are very popular in the gem trade.
Figure 8.
Raman spectra of the chrysoberyl host tested by three different lasers, 473, 532, and 785 nm.
3.7. FTIR Spectrum
Each sample was subjected to the FTIR transmission spectrum test, and 17 spectra
were recorded, among which the three representative spectra were displayed in Figure 9.
The FTIR features can be described as follows:
(1)
In the 2000–2500 cm
−1
range, two distinct peaks at 2405 and 2160 cm
−1
are present in
all samples, which can prove the samples as natural, differentiating them from the
synthetic counterparts; as a matter of fact, such a pattern was absent in the synthetic
chrysoberyl, as reported in the previous studies [22–26].
(2)
In the 2500–3000 cm
−1
range, several weak shoulders are observed at 2762, 2840,
and 2920, which could also be present in the synthetic material. Water and/or hy-
droxyl absorption bands in the 2500 to 3000 cm
−1
range may come from the hydrous
inclusions.
(3)
In the range between 3000 and 3500 cm
−1
, the 3223 peak is present in all sam-
ples, which can be accompanied by the 3112 shoulders of various strengths and
the 3301 cm−1, along with the 3412 and 3432 cm−1peaks.
Although chrysoberyl is well known in the gemological fields, the transmission FTIR
spectrum is not sufficiently studied as those of corundum, which is also an oxide mineral,
and the gem varieties ruby and sapphire are very popular in the gem trade.

Crystals 2023,13, 1580 10 of 17
Crystals 2023, 13, x FOR PEER REVIEW 11 of 18
Figure 9. Transmission FTIR spectra of the chrysoberyl investigated in this study.
3.8. UV-Vis and CIE Testing
While all the samples are subjected to the UV-Vis test to explore their coloration, their
typical spectra are selected to demonstrate their features in Figure 10. The 440 nm peak is
the most prominent in the spectrum, as it is the primary coloration origin, usually along
with a doublet peak at ~370 nm and a weak shoulder at 503 nm. The broad and weak band
at 650–660 nm may add a subtle hue shift, while the 340 nm in the blue range may also
result in a color shift. The abovementioned features agree with the previous study [14].
The 440 nm peak can be aributed to a trace of Fe substituting Al within the chrysoberyl
crystalline structure.
Figure 10. UV-Vis spectra of the chrysoberyl samples in this study.
3.9. The CIE Color Test
Figure 9. Transmission FTIR spectra of the chrysoberyl investigated in this study.
3.8. UV-Vis and CIE Testing
While all the samples are subjected to the UV-Vis test to explore their coloration, their
typical spectra are selected to demonstrate their features in Figure 10. The 440 nm peak is
the most prominent in the spectrum, as it is the primary coloration origin, usually along
with a doublet peak at ~370 nm and a weak shoulder at 503 nm. The broad and weak band
at 650–660 nm may add a subtle hue shift, while the 340 nm in the blue range may also
result in a color shift. The abovementioned features agree with the previous study [
14
].
The 440 nm peak can be attributed to a trace of Fe substituting Al within the chrysoberyl
crystalline structure.
Crystals 2023, 13, x FOR PEER REVIEW 11 of 18
Figure 9. Transmission FTIR spectra of the chrysoberyl investigated in this study.
3.8. UV-Vis and CIE Testing
While all the samples are subjected to the UV-Vis test to explore their coloration, their
typical spectra are selected to demonstrate their features in Figure 10. The 440 nm peak is
the most prominent in the spectrum, as it is the primary coloration origin, usually along
with a doublet peak at ~370 nm and a weak shoulder at 503 nm. The broad and weak band
at 650–660 nm may add a subtle hue shift, while the 340 nm in the blue range may also
result in a color shift. The abovementioned features agree with the previous study [14].
The 440 nm peak can be aributed to a trace of Fe substituting Al within the chrysoberyl
crystalline structure.
Figure 10. UV-Vis spectra of the chrysoberyl samples in this study.
3.9. The CIE Color Test
Figure 10. UV-Vis spectra of the chrysoberyl samples in this study.
3.9. The CIE Color Test
In order to establish a norm for color communication, the International Commission
on Illumination (CIE) created the L*a*b* color model in 1976. While a* and b* reflect
chromaticity with no set numerical boundaries, L* denotes lightness on a scale from zero to

Crystals 2023,13, 1580 11 of 17
one hundred, from black to white. Negative a* indicates green, positive a* indicates red,
negative b* symbolizes blue, and positive b* represents yellow.
We applied the CIE testing to all samples, and the results are displayed in Table 3,
including the L*, a*, b*, c*, and h* accordingly. The L* values range from 34.84 to 83.59, with
an average of 53.59, suggesting a medium to bright tone. While the a* value falls into the
range of
−
10.36 to
−
0.93, indicating a green hue. Meanwhile, the b* value ranges from 6.49
to 30.97, indicating a yellow-dominated hue. The L*, a*, and b* values combine, suggesting
the color of the samples studied is yellow with a tint of greenish secondary hue of medium
to bright tone, which agrees with the visual observation by the naked eye. The agreement
between the L*, a *, and b* values and visual observation proves that the CIELab method
could be an excellent tool to further explore the color of gemstones by quantifying the color.
Table 3. CIE color testing result of the seventeen samples in this study.
No. L* a* b* c* h*
G23001-1 50.25 −5.80 14.30 15.43 112.07
G23001-2 32.48 −3.74 9.95 10.63 110.59
G23001-3 43.00 −2.23 12.73 12.93 99.95
G23001-4 49.10 −2.82 11.46 11.80 103.82
G23001-5 43.38 −1.14 5.94 6.05 100.84
G23001-6 47.63 −3.89 11.21 11.86 109.12
G23001-7 54.79 −6.28 12.90 14.35 115.94
G23001-8 54.41 −6.36 15.64 16.89 112.14
G23001-9 41.43 −1.46 9.32 9.44 98.87
G23001-10 42.06 −0.93 6.49 6.56 98.19
G23001-11 67.86 −6.52 19.73 20.78 108.28
G23001-12 34.84 −3.68 16.32 16.73 102.70
G23001-13 83.59 −9.78 30.97 32.48 107.52
G23001-14 78.47 −10.36 24.97 27.04 112.53
G23001-15 59.74 −7.82 30.29 31.28 104.48
G23001-16 67.40 −6.39 30.03 30.70 102.02
G23001-17 60.57 −4.83 19.15 19.75 104.16
Average 53.59 −4.94 16.55 17.33 106.07
Standard
Deviation 14.50 2.84 8.15 8.51 5.40
Standard deviation measures the extent to which a set of values is dispersed from the
mean. A large standard deviation represents a large difference between most of the values
and their mean.
3.10. Luminescence and P.L.
Chrysoberyl is not well known for its luminescence properties, except for some alexan-
drite varieties, colored by Cr or V, exhibiting a distinct color-changing effect and usually
red fluorescence under 365 nm U.V. light. Interestingly, the canary yellow chrysoberyl in
this study was inert under 365 nm and 254 nm U.V. light; however, it showed green fluores-
cence detected by the SYNTHdetect machine, and such phenomena have not been reported
presently, according to the knowledge of the authors. Meanwhile, the photoluminescence
spectra were also performed in all the samples, and the prominent broad band centered
at 550 nm was distinct in samples showing strong green fluorescence. In comparison, the
550 nm band disappeared, and the 678 and 680 nm bands arose in samples with weak to
inert fluorescence, as shown in Figure 11.

Crystals 2023,13, 1580 12 of 17
Crystals 2023, 13, x FOR PEER REVIEW 13 of 18
centered at 550 nm was distinct in samples showing strong green fluorescence. In com-
parison, the 550 nm band disappeared, and the 678 and 680 nm bands arose in samples
with weak to inert fluorescence, as shown in Figure 11.
Figure 11. P.L. spectrum of chrysoberyl in this study can be classified into two paerns: a broad
band at 550 nm or two sharp peaks at 678 and 680 nm.
3.11. Chemical Results
All the samples have been subjected to chemical tests by EDXRF, and the chemical
results are displayed in Table 4, including Ti, V, Cr, Mn, Fe, Ga, and Sn. The samples in-
vestigated have high contents of titanium, tin and gallium; these abundances are in agree-
ment with the values generally found in natural chrysoberyls, while synthetic ones are
generally devoid of these elements [13]. While vanadium ranges from 60.9 to 133.5 ppm,
with an average of 94.08 ppm, chromium falls into the range of 23.6 to 84.5 ppm, with an
average value of 62.41 ppm. The V/Cr ratio fluctuates between 1.29 and 2.22, averaging at
1.56. By comparison, the Fe content is extremely high, ranging from 8781 to 19,500, aver-
aging at 11,295.88 ppm. The standard deviation of the value of each element was also listed
in Table 4, which could serve as a good indicator of the dispersion from their mean value.
Generally, the chemical results of all the samples in this study show similar features, they
are rich in Fe and poor in V and Cr.
Table 4. Chemical composition of the canary yellow chrysoberyl in this study detected EDXRF.
No. Ti V Cr Mn Fe Ga Sn Fe/Cr Fe/V Fe/(V + Cr) V/Cr
G23001-1 744 133.5 84.5 24.7 13,240 2070 814 156.69 99.18 60.73 1.58
G23001-2 121 86.1 67 24.3 8781 2093 781.5 131.06 101.99 57.35 1.29
G23001-3 177.5 113.5 77.2 26.1 8841 2689 51 114.52 77.89 46.36 1.47
G23001-4 245.4 82.5 47 30.4 9490 2625 55.6 201.91 115.03 73.28 1.76
G23001-5 221 60.9 30.4 28 8588 1989 83.3 282.50 141.02 94.06 2.00
G23001-6 220.7 54.5 24.6 26.7 10,270 1908 145 417.48 188.44 129.84 2.22
G23001-7 543.9 97.1 58.8 bdl
1 10,070 1956 560.4 171.26 103.71 64.59 1.65
G23001-8 216.2 89.3 50.9 bdl
1 11,170 2975 3461 219.45 125.08 79.67 1.75
G23001-9 266.9 105.7 74.9 27.9 10,870 3115 563.3 145.13 102.84 60.19 1.41
Figure 11.
P.L. spectrum of chrysoberyl in this study can be classified into two patterns: a broad band
at 550 nm or two sharp peaks at 678 and 680 nm.
3.11. Chemical Results
All the samples have been subjected to chemical tests by EDXRF, and the chemical
results are displayed in Table 4, including Ti, V, Cr, Mn, Fe, Ga, and Sn. The samples
investigated have high contents of titanium, tin and gallium; these abundances are in
agreement with the values generally found in natural chrysoberyls, while synthetic ones
are generally devoid of these elements [
13
]. While vanadium ranges from 60.9 to 133.5 ppm,
with an average of 94.08 ppm, chromium falls into the range of 23.6 to 84.5 ppm, with an
average value of 62.41 ppm. The V/Cr ratio fluctuates between 1.29 and 2.22, averaging
at 1.56. By comparison, the Fe content is extremely high, ranging from 8781 to 19,500,
averaging at 11,295.88 ppm. The standard deviation of the value of each element was also
listed in Table 4, which could serve as a good indicator of the dispersion from their mean
value. Generally, the chemical results of all the samples in this study show similar features,
they are rich in Fe and poor in V and Cr.
Table 4. Chemical composition of the canary yellow chrysoberyl in this study detected EDXRF.
No. Ti V Cr Mn Fe Ga Sn Fe/Cr Fe/V Fe/(V + Cr) V/Cr
G23001-1 744 133.5 84.5 24.7 13,240 2070 814 156.69 99.18 60.73 1.58
G23001-2 121 86.1 67 24.3 8781 2093 781.5 131.06 101.99 57.35 1.29
G23001-3 177.5 113.5 77.2 26.1 8841 2689 51 114.52 77.89 46.36 1.47
G23001-4 245.4 82.5 47 30.4 9490 2625 55.6 201.91 115.03 73.28 1.76
G23001-5 221 60.9 30.4 28 8588 1989 83.3 282.50 141.02 94.06 2.00
G23001-6 220.7 54.5 24.6 26.7 10,270 1908 145 417.48 188.44 129.84 2.22
G23001-7 543.9 97.1 58.8 bdl 110,070 1956 560.4 171.26 103.71 64.59 1.65
G23001-8 216.2 89.3 50.9 bdl 111,170 2975 3461 219.45 125.08 79.67 1.75
G23001-9 266.9 105.7 74.9 27.9 10,870 3115 563.3 145.13 102.84 60.19 1.41
G23001-10 113.9 105.9 84.4 25.1 12,010 3703 519.8 142.30 113.41 63.11 1.25
G23001-11 310.3 99.2 69.7 bdl 110,770 1722 130 154.52 108.57 63.77 1.42
G23001-12 227 85.2 58.3 bdl 111,450 1379 1260 196.40 134.39 79.79 1.46
G23001-13 58.6 91.5 64.7 24.1 10,890 3272 175.5 168.32 119.02 69.72 1.41
G23001-14 108.6 117.4 78.7 bdl 110,570 2880 309.7 134.31 90.03 53.90 1.49
G23001-15 509.6 97.1 65.7 bdl 119,500 1802 2500 296.80 200.82 119.78 1.48
G23001-16 1251 71.2 46.5 bdl 113,690 2288 320.4 294.41 192.28 116.31 1.53
G23001-17 612.8 108.8 77.6 bdl 111,830 2378 567.8 152.45 108.73 63.47 1.40
Average 349.91 94.08 62.41 26.37 11,295.88 2402.59 723.42 198.79 124.85 76.23 1.56
SD 2302.71 20.17 17.75 2.10 2553.23 629.91 925.22 80.43 36.26 24.55 0.25
1bdl = below the detection limit. 2SD = standard deviation.

Crystals 2023,13, 1580 13 of 17
4. Discussion
4.1. LabCIE Analysis
When the a* value decreases, both the value of b* and L* increase, as shown in Figure 12.
This means that as the stone becomes more green in color, its yellow and brightness will also
increase. Furthermore, the relations between L*, a*, and b* have been exploited regarding
a*-L*, a*-b*, and b*-L*, respectively. Linear analysis reveals their relations as follows:
a* = −0.1666L* + 3.9843, R2= 0.7243
b* = 0.4548L* −7.817, R2= 0.6538
b* = −2.4212a* + 4.5877, R2= 0.7099.
Crystals 2023, 13, x FOR PEER REVIEW 14 of 18
G23001-10 113.9 105.9 84.4 25.1 12,010 3703 519.8 142.30 113.41 63.11 1.25
G23001-11 310.3 99.2 69.7 bdl
1 10,770 1722 130 154.52 108.57 63.77 1.42
G23001-12 227 85.2 58.3 bdl
1 11,450 1379 1260 196.40 134.39 79.79 1.46
G23001-13 58.6 91.5 64.7 24.1 10,890 3272 175.5 168.32 119.02 69.72 1.41
G23001-14 108.6 117.4 78.7 bdl
1 10,570 2880 309.7 134.31 90.03 53.90 1.49
G23001-15 509.6 97.1 65.7 bdl
1 19,500 1802 2500 296.80 200.82 119.78 1.48
G23001-16 1251 71.2 46.5 bdl
1 13,690 2288 320.4 294.41 192.28 116.31 1.53
G23001-17 612.8 108.8 77.6 bdl
1 11,830 2378 567.8 152.45 108.73 63.47 1.40
Average 349.91 94.08 62.41 26.37
11,295.8
8 2402.59 723.42 198.79 124.85 76.23 1.56
SD 2 302.71 20.17 17.75 2.10 2553.23 629.91 925.22 80.43 36.26 24.55 0.25
1 bdl = below the detection limit. 2 SD = standard deviation.
4. Discussion
4.1. LabCIE Analysis
When the a* value decreases, both the value of b* and L* increase, as shown in Figure
12. This means that as the stone becomes more green in color, its yellow and brightness
will also increase. Furthermore, the relations between L*, a*, and b* have been exploited
regarding a*-L*, a*-b*, and b*-L*, respectively. Linear analysis reveals their relations as
follows:
a* = −0.1666L* + 3.9843, R2 = 0.7243
b* = 0.4548L* − 7.817, R2 = 0.6538
b* = −2.4212a* + 4.5877, R2 = 0.7099.
Figure 12 displays the correlation between the three parameters. The a*-L* diagram
shows a negative correlation, where the L* increases while the a* value decreases. The
linear analysis shows a trend line consisting of a* and L* values, giving a formula as a* =
−0.1666L* + 3.9843, and the correlation coefficient R2 being 0.7243. The b*-L* diagram
demonstrates that b* and L* are positively correlated as the b* value increases together
with the L* value. The linear analysis resulted in a formula as follows: b* = 0.4548L* −
7.817, R2 = 0.6538. Meanwhile, the a*-b* diagram shows that a* negatively correlates with
b*, with the linear formula as b* = −2.4212a* + 4.5877, and the correlation coefficient R2 =
70.99%.
(a) (b) (c)
Figure 12. The CIELAB is ploing regarding the L*, a*, and b* values, respectively, the relationship
between a* and L* (a), the relationship between b* and L* (b), the relationship between a* and b*
(c).
The linear relations among the a*, b*, and L* can also be ploed in a 3D model, as
shown in Figure 13. The close relationship among the three parameters may serve as a
Figure 12.
The CIELAB is plotting regarding the L*, a*, and b* values, respectively, the relationship
between a* and L* (
a
), the relationship between b* and L* (
b
), the relationship between a* and b* (
c
).
Figure 12 displays the correlation between the three parameters. The a*-L* diagram
shows a negative correlation, where the L* increases while the a* value decreases. The
linear analysis shows a trend line consisting of a* and L* values, giving a formula as
a* = −0.1666L* + 3.9843
, and the correlation coefficient R
2
being 0.7243. The b*-L* diagram
demonstrates that b* and L* are positively correlated as the b* value increases together with
the L* value. The linear analysis resulted in a formula as follows:
b* = 0.4548L* −7.817
,
R2= 0.6538.
Meanwhile, the a*-b* diagram shows that a* negatively correlates with b*, with
the linear formula as b* = −2.4212a* + 4.5877, and the correlation coefficient R2= 70.99%.
The linear relations among the a*, b*, and L* can also be plotted in a 3D model, as
shown in Figure 13. The close relationship among the three parameters may serve as a good
indicator to further exploit the color measurement and advance our understanding of the
canary yellow color, which contributes to the popularity of chrysoberyl in the gem trade.

Crystals 2023,13, 1580 14 of 17
Crystals 2023, 13, x FOR PEER REVIEW 15 of 18
good indicator to further exploit the color measurement and advance our understanding
of the canary yellow color, which contributes to the popularity of chrysoberyl in the gem
trade.
Figure 13. The 3D ploing of CIE data regarding L, a*, and b*.
4.2. Chemical Features and Color
V, Cr, and Fe are the main color agents in chrysoberyl. In the samples in this study,
V and Cr show a very close correlation, as displayed in Figure 14. Considering the ratio
among Fe, V, and Cr, the Fe/Cr, Fe/V, and Fe/(V + Cr) are calculated based on these three
element values since they contribute to the color of chrysoberyl accordingly. The linear
formula of V vs. Cr shows that as follows:
V = 0.8225 × Cr − 14.98, R
2
= 0.8736
Fe/V =0.4057 × Fe/Cr + 44.202, R
2
= 0.81
The trace amount of V can result in the green hue in the samples, but in a very subtle
way, while the Cr is too low to contribute a distinct hue. Through comparison, Fe gives
rise to the yellow hue. The contents of V and Cr are at a similar level, but the Fe is much
higher than that of V, Cr, or the sum of V and Cr. As listed in Table 4, the Fe/Cr ranges
from 131.06 to 417.48, averages 198.79, and the S.D. value is 80.43. The Fe/V ranges from
77.89 to 200.82, with an average value of 124.85 and an SD of 36.26. Additionally, the Fe/(V
+ Cr) ranges from 46.36 to 129.84, averages 76.23, and the standard deviation is 24.55.
Regarding the standard deviation value, it is interesting to point out that the S.D. of
Fe/(Cr + V) is lower than both that of Fe/Cr and Fe/V. V and Cr share chemical features in
common, as they both belong to the first transition series. A recent study has revealed the
effects of such mi nute le vels o f vana dium an d/or chromium on somewhat greenish-yellow
chrysoberyls from Madagascar and Sri Lanka [27]. So, it is reasonable to take them into
consideration as a whole. Based on the content of Fe, V, and Cr, together with their relative
ratios, the green component is usually covered by the yellow hue due to abundant Fe.
Figure 13. The 3D plotting of CIE data regarding L, a*, and b*.
4.2. Chemical Features and Color
V, Cr, and Fe are the main color agents in chrysoberyl. In the samples in this study,
V and Cr show a very close correlation, as displayed in Figure 14. Considering the ratio
among Fe, V, and Cr, the Fe/Cr, Fe/V, and Fe/(V + Cr) are calculated based on these three
element values since they contribute to the color of chrysoberyl accordingly. The linear
formula of V vs. Cr shows that as follows:
V = 0.8225 ×Cr −14.98, R2= 0.8736
Fe/V =0.4057 ×Fe/Cr + 44.202, R2= 0.81
Crystals 2023, 13, x FOR PEER REVIEW 16 of 18
Hence, the sample exhibits yellow as the primary hue, accompanied by a general green
hue.
(a) (b)
Figure 14. The ploing of V versus Cr (a) and Fe/V versus Fe/Cr (b).
4.3. Inclusions and Geological Implications
The geological occurrence of chrysoberyl has been summarized by previous studies
[28,29]. The chrysoberyl deposits can be classified into four categories: melt crystallization,
metamorphism, metasomatism, and weathering. The minerals detected in samples in this
study include quar, sillimanite, muscovite, and calcite. The well-formed crystalline habit
of sillimanite contracts with the irregular shapes of muscovite and quar.
According to the previous study [30], before the crystallization of chrysoberyl, it is
possible that sillimanite formed due to the consumption of quar and muscovite follow-
ing the formula: “Muscovite + quar + H2O = sillimanite.” The phase diagram proposed
by the authors demonstrates that the granite pegmatite-related chrysoberyl formed at a
temperature of 800–900 °C and a pressure of 0.7–0.8 GPa [31,32]. The association minerals
suggest the samples in this study originate from the muscovite–quar–sillimanite–calcite
granite pegmatite.
5. Conclusions
In this study, microscopic observation together with Raman spectroscopy on canary
yellow chrysoberyl samples revealed the presence of a combination of various minerals
such as quar, muscovite, carbon and sillimanite, which may help explain the geological
origin of chrysoberyl itself. CIE testing has proven to be a very useful tool to decode the
aractive canary yellow color, showing linear relations among the a*, b*, and L* values of
the CIELab results derived from the samples. Furthermore, the chemical results showed a
very good correlation between Cr and V, and both of them are at a low level; Fe is respon-
sible for the canary yellow color, which also agrees with the evidence of the UV-Vis spec-
trum. Raman tests have shown that the peak at 930 cm−1 is very distinct and therefore can
be used to identify chrysoberyl, both as a gem and as an inclusion, regardless of the ap-
plied laser wavelength. In general, the gemological, spectral, and chemical features of the
canary yellow chrysoberyl investigated in this work have provided more valuable data
for gemology and mineralogy and may help further advance our understanding of this
gem variety.
Author Contributions: Writing—original draft, Y.G. and X.L.; writing—review and editing, Y.G.,
R.T. and T.H.; data curation, Y.G., X.L. and Y.C.; software, Y.G. and K.L.; methodology, Y.G., X.L.,
R.T. and B.X. All authors have read and agreed to the published version of the manuscript.
Figure 14. The plotting of V versus Cr (a) and Fe/V versus Fe/Cr (b).
The trace amount of V can result in the green hue in the samples, but in a very subtle
way, while the Cr is too low to contribute a distinct hue. Through comparison, Fe gives

Crystals 2023,13, 1580 15 of 17
rise to the yellow hue. The contents of V and Cr are at a similar level, but the Fe is much
higher than that of V, Cr, or the sum of V and Cr. As listed in Table 4, the Fe/Cr ranges from
131.06 to 417.48, averages 198.79, and the S.D. value is 80.43. The Fe/V ranges from 77.89 to
200.82, with an average value of 124.85 and an SD of 36.26. Additionally, the
Fe/(V + Cr)
ranges from 46.36 to 129.84, averages 76.23, and the standard deviation is 24.55.
Regarding the standard deviation value, it is interesting to point out that the S.D. of
Fe/(Cr + V) is lower than both that of Fe/Cr and Fe/V. V and Cr share chemical features in
common, as they both belong to the first transition series. A recent study has revealed the
effects of such minute levels of vanadium and/or chromium on somewhat greenish-yellow
chrysoberyls from Madagascar and Sri Lanka [
27
]. So, it is reasonable to take them into
consideration as a whole. Based on the content of Fe, V, and Cr, together with their relative
ratios, the green component is usually covered by the yellow hue due to abundant Fe.
Hence, the sample exhibits yellow as the primary hue, accompanied by a general green
hue.
4.3. Inclusions and Geological Implications
The geological occurrence of chrysoberyl has been summarized by previous stud-
ies
[28,29]
. The chrysoberyl deposits can be classified into four categories: melt crystalliza-
tion, metamorphism, metasomatism, and weathering. The minerals detected in samples in
this study include quartz, sillimanite, muscovite, and calcite. The well-formed crystalline
habit of sillimanite contracts with the irregular shapes of muscovite and quartz.
According to the previous study [
30
], before the crystallization of chrysoberyl, it is
possible that sillimanite formed due to the consumption of quartz and muscovite following
the formula: “Muscovite + quartz + H
2
O = sillimanite.” The phase diagram proposed
by the authors demonstrates that the granite pegmatite-related chrysoberyl formed at a
temperature of 800–900
◦
C and a pressure of 0.7–0.8 GPa [
31
,
32
]. The association minerals
suggest the samples in this study originate from the muscovite–quartz–sillimanite–calcite
granite pegmatite.
5. Conclusions
In this study, microscopic observation together with Raman spectroscopy on canary
yellow chrysoberyl samples revealed the presence of a combination of various minerals
such as quartz, muscovite, carbon and sillimanite, which may help explain the geological
origin of chrysoberyl itself. CIE testing has proven to be a very useful tool to decode the
attractive canary yellow color, showing linear relations among the a*, b*, and L* values of
the CIELab results derived from the samples. Furthermore, the chemical results showed
a very good correlation between Cr and V, and both of them are at a low level; Fe is
responsible for the canary yellow color, which also agrees with the evidence of the UV-Vis
spectrum. Raman tests have shown that the peak at 930 cm
−1
is very distinct and therefore
can be used to identify chrysoberyl, both as a gem and as an inclusion, regardless of the
applied laser wavelength. In general, the gemological, spectral, and chemical features of
the canary yellow chrysoberyl investigated in this work have provided more valuable data
for gemology and mineralogy and may help further advance our understanding of this
gem variety.
Author Contributions:
Writing—original draft, Y.G. and X.L.; writing—review and editing, Y.G., R.T.
and T.H.; data curation, Y.G., X.L. and Y.C.; software, Y.G. and K.L.; methodology, Y.G., X.L., R.T. and
B.X. All authors have read and agreed to the published version of the manuscript.
Funding: This research received no external funding.
Data Availability Statement: The data presented in this study are available in the article.
Acknowledgments:
Huixin Zhao and Qi Han are thanked for their help during the photography and
equipment testing. The authors are very grateful to the reviewers who helped improve this article.

Crystals 2023,13, 1580 16 of 17
Conflicts of Interest:
The authors declare no conflict of interest. Author Yujie Gao was employed
by the company Guild Gem Laboratories. The remaining authors declare that the research was
conducted in the absence of any commercial or financial relationships that could be construed as a
potential conflict of interest.
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