Osumilite-(Mg): Validation as a Mineral Species and New Data

Abstract

Osumilite-(Mg), the Mg-dominant analogue of osumilite, has been approved by the CNMNC IMA as a new mineral species. The holotype sample has been found at Bellerberg, Eifel volcanic area, Germany. Fluorophlogopite, sanidine, cordierite, mullite, sillimanite, topaz, pseudobrookite and hematite are associated minerals. Osumilite-(Mg) occurs as short prismatic or thick tabular hexagonal crystals reaching 0.5 × 1 mm in size in the cavities in basaltic volcanic glasses at their contact with thermally metamorphosed xenoliths of pelitic rocks. The mineral is brittle, with Mohs’ hardness 6.5. Cleavage was not observed. Color is blue to brown. D
meas = 2.59(1), D
calc = 2.595 g/cm3. No bands corresponding to H2O and OH-groups are in the IR spectrum. Osumilite-(Mg) is uniaxial (+), ω = 1.539(2), ɛ = 1.547(2). The chemical composition (electron microprobe, average of 5 point analyses, wt %) is: 0.08 Na2O, 3.41 K2O, 0.04 CaO, 7.98 MgO, 0.28 MnO, 21.57 Al2O3, 3.59 Fe2O3, 62.33 SiO2, total 99.28. The empirical formula is: (K0.72Na0.03Ca0.01)(Mg1.97Mn0.04)[Al4.21Fe
0.453+Si10.32]O30. The simplified formula is: KMg2Al3(Al2Si10)O10. The crystal structure was refined on a single crystal, R = 0.0294. Osumilite-(Mg) is hexagonal, space group P6/mcc; a = 10.0959(1), c = 14.3282(2)Å, V = 1264.79(6) Å3, Z = 2. The strongest reflections in the X-ray powder diffraction pattern [d, Å I %) (hkl)] are: 7.21 (37) (002), 5.064 (85) (110), 4.137 (45) (112), 3.736 (43) (202), 3.234 (100) (211), 2.932 (42) (114), 2.767 (51) (204). A type specimen is deposited in the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow, registration number 4174/1.

Full text

ISSN 10757015, Geology of Ore Deposits, 2012, Vol. 54, No. 8, pp. 656–662. © Pleiades Publishing, Ltd., 2012.
Original Russian Text © N.V. Chukanov, R.K. Rastsvetaeva, S.M. Aksenov, I.V. Pekov, N.V. Zubkova, S.N. Britvin, D.I. Belakovskiy, W. Schüller, B. Ternes, 2012, published in
Zapiski Rossiiskogo Mineralogicheskogo Obshchestva, 2012, No. 1, pp. 71–79.
656
1
INTRODUCTION
The topological diversity of tetrahedral layers, pri
marily composed of silicate and aluminosilicate tetra
hedra, is great in the structures of minerals (
Mineraly
,
1992) and permanently increases. In particular, the
crystal structures of three hydrous calcalkaline sili
cates comprising the mountainite family were solved
recently: proper mountainite KNa
2
Ca
2
[Si
8
O
19
(OH)]
⋅
6H
2
O (Zubkova et al., 2009) and related new minerals
shlykovite KCa[Si
4
O
9
(OH)]
⋅
3H
2
O and cryptophyllite
1
The new mineral species günterblassite and its name were
approved by the Commission on New Minerals, Nomenclature,
and Mineral Classification of the International Mineralogical
Association on June 2, 2011 (IMA no. 2011032).
2
Corresponding author: N.V. Chukanov. Email: chukanov@
icp.ac.ru
K
2
Ca[Si
4
O
l0
]
⋅
5H
2
O (Pekov et al., 2010; Zubkova et
al., 2010). In these minerals, the eight and fourtetra
hedra rings that are similar to those in apophyllite, but
differ in their orientation of tetrahedra can be distin
guished within the [Si
8
Ø
20
] layer (where Ø = O, OH).
The individual feature of the mountainitefamily min
erals is the position of the pendant (not shared with
other tetrahedra) apex of one of Sitetrahedra in the
fourmember ring opposite to the direction of other
three apices relative to the plane of the layer. In shlyk
ovite and cryptophyllite, all fourmembered rings in
the layer have the same orientation (the shlykovite
type layer), whereas in mountainite, the layer consists
of alternating chains of such rings rotated 180° relative
to each other (Zubkova et al., 2010).
Günterblassite, (K,Ca)
3–
x
Fe[(Si,Al)
13
O
25
(OH,O)
4
]
⋅
7H
2
O, a New
Mineral: the First Phyllosilicate with Triple Tetrahedral Layer
1
N. V. Chukanov
a
, R. K. Rastsvetaeva
b
, S. M. Aksenov
b
, I. V. Pekov
c
, N. V. Zubkova
c
,
S. N. Britvin
d
, D. I. Belakovskiy
e
, W. Schüller
f
, and B. Ternes
g
a
Institute of Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka, Moscow oblast, 142432 Russia
b
Institute of Crystallography, Russian Academy of Sciences, Leninskii pr. 59, Moscow, 117333 Russia
c
Faculty of Geology, Moscow State University, Moscow, 119991 Russia
d
Faculty of Geology, St. Petersburg State University, Universitetskaya nab. 7/9, St Petersburg, 199034 Russia
e
Fersman Mineralogical Museum of the Russian Academy of Sciences, Leninskii pr. 82, Moscow, 117071 Russia
f
Straussenpesch 22, 53518 Adenau, Germany
g
Bahnhofstrasse 45, 56727 Mayen, Germany
Received September 22, 2011
Abstract
—A new mineral, günterblassite, has been found in the basaltic quarry at Mount Rother Kopf near
Gerolstein, Rheinland–Pfalz, Germany as a constituent of the late assemblage of nepheline, leucite, augite,
phlogopite, åkermanite, magnetite, perovskite, a lamprophyllitegroup mineral, götzenite, chabaziteK,
chabaziteCa, phillipsiteK, and calcite. Günterblassite occurs as colorless lamellar crystals up to 0.2
×
1
×
1.5 mm in size and their clusters. The mineral is brittle, with perfect cleavage parallel to (001) and less perfect
cleavage parallel to (100) and (010). The Mohs hardness is 4. The calculated and measured density is 2.17 and
2.18(1) g/cm
3
, respectively. The IR spectrum is given. The new mineral is optically biaxial and positive as fol
lows:
α
= 1.488(2),
β
= 1.490(2),
γ
= 1.493(2), 2
V
meas
= 80(5)°. The chemical composition (electron micro
probe, average of seven point analyses, H
2
O is determined by gas chromatography, wt %) is as follows:
0.40 Na
2
O, 5.18 K
2
O, 0.58 MgO, 3.58 CaO, 4.08 BaO, 3.06 FeO, 13.98 Al
2
O
3
, 52.94 SiO
2
, 15.2 H
2
O, and
the total is 98.99. The empirical formula is Na
0.15
K
1.24
Ba
0.30
Ca
0.72
Mg
0.16
F[Si
9.91
Al
3.09
O
25.25
(OH)
3.75
]
⋅
7.29H
2
O. The crystal structure has been determined from a single crystal,
R
= 0.049. Günterblassite is orthor
hombic, space group
Pnm
2
1
; the unitcell dimensions are
a
= 6.528(1),
b
= 6.970(1),
c
= 37.216(5) Å,
V
=
1693.3(4) Å
3
,
Z
= 2. Günterblassite is a member of a new structural type; its structure is based on threelayer
block [Si
13
O
25
(OH,O)
4
]. The strong reflections in the Xray powder diffraction pattern [
d
Å (
I
, %) are as fol
lows: 6.532 (100), 6.263 (67), 3.244 (49), 3.062 (91), 2.996 (66), 2.955 (63), and 2.763 (60). The mineral was named
in honor of Günter Blass (born in 1943), a wellknown amateur mineralogist and specialist in electron microprobe
and Xray diffraction. The type specimen of günterblassite is deposited in the collections of the Fersman Mineral
ogical Museum of the Russian Academy of Sciences, Moscow, Russia, with the registration number 4107/1.
DOI:
10.1134/S1075701512080065
e0.48
2+
NEW MINERALS

GEOLOGY OF ORE DEPOSITS
Vol. 54
No. 8
2012
GÜNTERBLASSITE, (K,Ca)
3
– XFE[(Si,Al)
13
O
25
(OH,O)
4
]
Þ
7H
2
O657
Two shlykovite layers shared by apices of tetrahedra
form a specific double layer, known as a twolayer tet
rahedral packet, or module [Si
8
Ø
19
], where Ø = O,
OH. This layer is known from the structures of rhode
site K
1–
x
Na
x
+2
y
Ca
2–
y
[Si
8
O
18
(OH)]
⋅
(6 –
z
)H
2
O,
macdonaldite BaCa
4
[Si
8
O
18
(OH)]
2
⋅
10H
2
O, seidite
(Ce) Na
4
(Ce,Sr)
2
Ti[Si
8
O
18
(OH)](O,OH,F)
5
⋅
5H
2
O,
and monteregianite(Y) KNa
2
Y[Si
8
O
19
]
⋅
5H
2
O. Sim
ilar but aluminosilicate double layers occur in del
hayelite K
4
Na
2
Ca
2
[Si
7
AlO
19
]F
2
Cl, fivegite
K
4
Ca
2
[Si
7
AlO
17
(O
2–
x
OH
x
]Cl, and hydrodelhayelite
KCa
2
[Si
7
AlO
17
(OH)
2
](H
2
O)
6–
x
(Ferraris and Gula,
2005; Pekov et al., 2009, 2011a). All these minerals
and related synthetic compounds are combined into
the rhodesite meroplesiotype series, in which the alu
minosilicate branch, i.e., the delhayelite family, is dis
tinguished (Cadoni and Ferraris, 2009; Pekov et al.,
2011b).
The new mineral species described in this article is
the first phyllosilicate with a triple tetrahedral layer
(triplelayer tetrahedral packet, or module). The min
eral was named günterblassite in honor of Günter
Blass (born in 1943), a wellknown amateur mineral
ogist and specialist in electron microprobe and Xray
diffraction analyses who has carried out many analyses
of minerals (predominantly from the Eifel region) and
is the coauthor of descriptions of several new mineral
species, including pattersonite, allanpringite, schäfer
ite, lukrahnite, hechtsbergite, ferriallanite(La),
windhoekite, and perrierite(La).
The type specimen of günterblassite is deposited in
the collections of the Fersman Mineralogical Museum
of the Russian Academy of Sciences, Moscow, Russia
with the registration number 4107/1.
OCCURRENCE
The specimens with günterblassite were collected
in 2010 in the operating basaltic quarry at Mount
Rother Kopf, Roth community, near Gerolstein,
Rheinland–Pfalz, Germany. The new mineral was
discovered as a member of the late mineral assemblage
that consists of nepheline, leucite, augite, phlogopite,
akermanite, magnetite, perovskite, barium minerals of
the lamprophyllite group, götzenite, and fluorapatite,
after which the lowtemperature chabaziteK, chaba
ziteCa, phillipsiteCa, and calcite crystallized. The
crystals of all these minerals encrust the walls of miar
oles in alkali basalt.
MORPHOLOGY AND PHYSICAL PROPERTIES
Günterblassite occurs as flattened from thin lamel
lar to tabular crystals up to 0.2
×
1
×
1.5 mm in size
(Fig. 1) and their nearparallel or sheafshaped aggre
gates up to 3 mm across. Simply faced crystals, such as
rectangular lamellae or plates formed only by the faces
of three pinacoids, are the most typical, i.e., {001}
(major habit form), {010} and {100} (side faces). These
crystals are supplemented by less common faces of
rhombic prism {110} and the {
h
0
l
} and/or {0
kl
} face
belts, which are uneven and convex and, thus, difficult
to measure and index. The epitactic or more frequent
syntactic intergrowth of the new mineral with
nepheline and the lamprophyllitegroup members are
common (Fig. 2). The {001} faces of günterbalssite are
Fig. 1.
Crystals of günterblassite. Width of image is 3 mm. Photo by V. Betz.

658
GEOLOGY OF ORE DEPOSITS
Vol. 54
No. 8
2012
CHUKANOV et al.
parallel (coplanar) to {100} faces and occasionally
{001} of nepheline and {001} of the lamprophyllite
type minerals. Irregular intergrowths of the new min
eral and nepheline or leucite are observed frequently.
Günterblassite is usually colorless and watertrans
parent; occasionally, its crystals are white, pale yellow,
or brown; the streak is white. The mineral is brittle
with Mohs hardness 4; the perfect cleavage is parallel
to (001) and less perfect, to (100) and (010). The calcu
lated density is 2.17 g/cm
3
, while the density measured by
equilibration in heavy liquids is 2.18(1) g/cm
3
.
Wide bands in the IR spectrum of günterblassite
(Fig. 3) reflect cation disordering in the structure (see
below). Absorption bands and their assignments are as
follows (given in cm
–1
; s is strong band and sh is shoul
der): 3610sh, 3400s, 3230sh (O–H stretching vibra
tions); 1650 (bending vibrations of H
2
O molecules);
1175sh, 1037s, 900sh (Si–O stretching vibrations);
780sh, 704, 630sh, 596 (O–Si–O bending vibrations);
and 442s, 380sh (combination of Si–O–Si bending
vibrations and stretching vibrations of the
M
O
7
poly
hedra, where
M
= Fe
2+
, Ca, Mg).
Bands of B and Cbearing groups between 1200
and 1500 cm
–1
are not detected in the IR spectrum of
günterblassite.
The new mineral is optically biaxial, positive:
α
=
1.488(2),
β
= 1.490(2),
γ
= 1.493(2), 2
V
meas
= 80(5)°,
2
V
calc
= 79°. No dispersion of the optical axes is
observed. The optical orientation is
Z
=
c
; axes of opti
cal indicatrix are perpendicular to cleavage planes.
CHEMICAL COMPOSITION
The chemical composition of günterblassite was
determined on a Tescan Vega II XMU SEM equipped
with an INCAxsight EDS that operate on a tungsten
cathode at an accelerating voltage of 15.7 kV. The cur
rent of the absorbed electrons on Co was 0.5 nA. The
angle of selection of Xray radiation was 35° and the
focal distance between the sample and detector was
25 mm.
Fig. 2.
Intergrowth of günterblassite with a lamprophyllitegroup mineral. Width of image is 3 mm. Photo by V. Betz.
30002000
1000 cm
–1
380
442
630 596
780 704
900
1037
1175
1650
3230
3400
3610
Fig. 3
, IR spectrum of günterblassite.

GEOLOGY OF ORE DEPOSITS
Vol. 54
No. 8
2012
GÜNTERBLASSITE, (K,Ca)
3
– XFE[(Si,Al)
13
O
25
(OH,O)
4
]
Þ
7H
2
O659
The H
2
O content was measured via gas chromatog
raphy of the annealing products at 1400°C with a vario
MICRO cube instrument.
The measured chemical composition (wt %) is given in
Table 1. The empirical formula of günterblassite calculated
based on (Si,Al)
13
(O,OH)
29
(according to the structural
data) is Na
0.15
K
1.24
Ba
0.30
Ca
0.72
Mg
0.16
F[Si
9.91
Al
3.09
O
25.25
(OH)
3.75
]
⋅
7.29H
2
O. The idealized formula is
(K,Ca)
3
Fe[(Si,Al)
13
O
25
(OH,O)
4
]
⋅
7H
2
O.
XRAY CRYSTALLOGRAPHY AND CRYSTAL
STRUCTURE
The Xray powder diffraction pattern of günter
balssite (Table 2) was recorded on a Stoe IPDS II sin
glecrystal diffractometer with an image plate detec
tor, Mo
K
α
radiation, an accelerating voltage of 45 kV,
and a current of 30 mA. The measurements were car
ried out using the Gandolfi method by rotation around
two axes (
ω
and
ϕ
); the distance between the sample
and detector was 200 mm and the measurement time
was 60 min.
All reflections of the Xray powder diffraction pat
tern of günterblasite are readily indexed in the orthor
hombic unit cell with the following unitcell dimen
sions refined by the least squares method:
a
=
6.522(8),
b
= 6.972(8),
c
= 37.21(4) Å, and
V
=
1692(6) Å
3
.
The Xray singlecrystal data were collected with
an Xcalibur CCD diffractometer and Mo
K
α
radiation.
The orthorhombic (space group
Pnm
2
1
) unitcell
dimensions from these data are as follows:
a
=
6.528(1),
b
= 6.970(1),
c
= 37.216(5) Å,
V
= 1693.3(4)
Å
3
, and
Z
= 2.
The crystal structure of the new mineral was solved
using 2706 unique reflections with |F| > 3
σ
(
F
),
R
=
0.049. Detailed structural data on günterblassite have
been reported by Rastsvetaeva et al. (2012); only a
brief characterization is given below.
The structure of the new mineral is based on a tri
plelayered packet (module) [
T
13
O
25
(OH,O)
4
], where
e0.48
2+
T
= Si, Al (Fig. 4). The module consists of three SiO
layers that are shared by apices of Sitetrahedra and
pierced by zeolite channels in the [010] and [100]
directions. Si and Al atoms are disordered in the
packet. The outer shlykovitetype layers
[
T
24
O
9
(O,OH)] differ from the inner [
T
5
O
11
] layer in
an additional tetrahedron SiO
4
.
Unlike the minerals of the mountainite and del
hayelite families, where the columns of completely
occupied edgeshared Cacentred octahedra are
pressed between the tetrahedral layers (packets)
(Cadoni and Ferraris, 2009; Pekov et al., 2011b), in
the structure of günterblassite, cations of moderate
force strengths (Fe, Mg, Ca) form isolated septatopes
(Fe,Ca,Mg)[O
2
(OH)
2
(H
2
O)
3
] (with the cation–anion
distance ranging from 2.380 to 2.726 Å), which sew
tetrahedral packets together to form an original het
eropolyhedral framework (Fig. 5). K, Ba, Na, and par
tially Ca ions and coordinating H
2
O molecules reside
in interlayer and fill channels in the triplelayered
packet. The extra framework sites are partially vacant.
Table 1.
Chemical composition of günterblassite (average
of seven microprobe point analyses)
Component Content, wt
%Range of
contents Standard
Na
2
O 0.40 0.14–0.67 Albite
K
2
O 5.18 4.28–5.91 Microcline
MgO 0.58 0.42–0.81 Diopside
CaO 3.58 2.99–3.89 Wollastonite
BaO 4.07 3.55–5.08 BaF
2
FeO 3.06 2.43–3.85 Fe
2
O
3
Al
2
O
3
13.98 13.60–14.26 Al
2
O
3
SiO
2
52.94 52.20–54.23 SiO
2
H
2
O15.2
Total 98.99
Note: F, P, S, Cl, Ti, Cr, Mn, and Sr contents are below detection
limits.
c
ab
Fig. 4.
Triple tetrahedral packet of günterblassite.

660
GEOLOGY OF ORE DEPOSITS
Vol. 54
No. 8
2012
CHUKANOV et al.
DISCUSSION
Günterblassite is not only a member of the new
structural type, but the first known mineral with triple
layered tetrahedral SiO packet The discovery of this
mineral outlines a special polysomatic series that links
phyllosilicates and phylloaluminosilicates with tecto
silicates. The degree of condensation of the tetrahe
dral (Si,Al)O motif progressively increases from the
singlelayer silicates of the mountainite family via
doublelayered silicates and aluminosilicates of the
Table 2.
Xray powder diffraction data of günterblassite
I
meas
,%
d
meas
, Å
I
calc
,%
d
calc
, Å*
hkl
13 9.30 15 9.304 004
45 6.885 46 6.851 011
100 6.523 95 6.528 100
67 6.263 37,64 6.430, 6.203 101, 006
13 5.843 3 5.777 103
4 5.388 19 5.344 104
23 5.116 23 5.088 015
42 4.789 27.18 4.908, 4.765 105, 110
33 4.508 19 4.497 106
13 4.215 21 4.227 017
14 4.070 3 4.122 107
15 4.021 3 4.013 112
7 3.763 7, 29 3.779, 3.722 116, 0.0.10
15 3.550 19, 7 3.556, 3.548 019, 117
8 3.488 12 3.485 020
49 3.244 13, 28, 26, 12 3.264, 3.252, 3.233.,3.215 024, 201,1.0.10, 202
91 3.062 22, 11, 73, 17, 14, 16 3.080, 3.074, 3.064, 3.044, 3.038, 3.033 204, 120, 121, 0.1.11, 026, 122
66 2.996 56, 11, 15 3.004, 2.989, 2.984 1.0.11, 205, 123
63 2.955 5, 28, 19, 7, 45 2.956, 2.947, 2.933, 2.919, 2.919 210, 211, 1.1.10, 212, 124
51 2.853 18, 7, 91, 13 2,889, 2.875, 2.842, 2.817 206, 213, 125, 214
60 2.763 100, 39, 19 2.759, 2.755, 2.747 1.1.11, 126, 215
18 2.676 19 2.668 216
7 2.599 5 2.599 1.1.12
8 2.193 21, 9, 4 2.191, 2.189, 2.183 1.0.16, 130, 1.2.12
5 2.070 5, 3, 1, 2 2.077, 2.074, 2.068, 2.064 310, 311, 0.0.18, 2.2.10
4 2.013 5, 5, 3, 4 2.027, 2.026, 2.014, 2.006 314, 039, 307, 2.2.10
3 1.950 8, 23, 3 1,970, 1.948, 1.935 316, 2.2.11, 0.2.16
5 1.892 11, 2, 3, 4, 3 1.900, 1.897, 1.894, 1.893, 1.889 2.1.15, 1.1.18, 2.0.16, 230, 2.2.12
7 1.848 12 1.846 320
5 1.811 4, 1, 8 1.814, 1,812, 1.810 3.1.10,1.1.19,236
2 i.776 1, 2 1.781, 1.7S9 3.0.12, 2.1.17
5 1.745 1, 3, 31, 1 1.747, 1.744, 1.743.1,739 2.0.18, 327, 040, 1.3.13
6 1.692 5, 12, 1 1.696, 1.692, 1.690 0.3.15, 0.0.22, 1.3.14
6 1.662 11, 2 1.664, 1.661 2.2.16.1.1.21
5 1.593 3, 2, 4, 2, 5 1.594, 1.594, 1.594, 1.593, 1.592 1.1.22, 405, 1.3.16, 0.3.17, 1.2.20
6 1.544 7 1.543 3.0.17
3 1.532 2 1.532 242
4 1.516 5 1.517 244
* Calculated from structural data. The reflections with intensity
≥
1 are given for the calculated Xray powder diffraction pattern.

GEOLOGY OF ORE DEPOSITS
Vol. 54
No. 8
2012
GÜNTERBLASSITE, (K,Ca)
3
– XFE[(Si,Al)
13
O
25
(OH,O)
4
]
Þ
7H
2
O661
c
b
Fe K
Fig. 5.
The structure of interlayer part of günterblassite. H
2
O molecules occupy pendant (not shared with tetrahedra) apices of
the Fepolyhedron.
Table 3.
Comparative data of günterblassite and related minerals
Parameter Shlykovite Rhodesite Günterblassite
Formula K
2
Ca
2
[Si
8
O
18
(OH)
2
]
⋅
6H
2
OHK
1–
x
Na
x
+2
y
Ca
2–
y
×
[Si
8
O
19
]
×
(6 –
z
)H
2
O(K,Ca, Ba,Na,
䊐
)
3
Fe[(Si,Al)
13
×
O
25
(OH.O)
4
]
⋅
7H
2
O
Symmetry, space group Monoclinic,
P
2
1
/
c
Orthorhombic,
Pmam
Orthorhombic,
Pnm
2
1
Unitcell dimensions
a
, Å 6.490 7.01–7.06 6.528
b
, Å 6.997 6.54–6.59 6.970
c
. Å 26.714 23.4–23.8* 37.216
β
, * 94.60 90 90
V
, Å
2
1209 1082–1098 1693.3
Z
22 2
Number of layers in the
tetrahedral module 11 3.4
Strong reflections of the
Xray powder diffraction
pattern:
d
, Å –
I
%
13.33–100 6.55–100 6.S85–45
6.67–76 6.30–32 6.523–100
6.47–55 5.90–34 6.263–67
3469–45 5.032–28 4.789–42
3.068–57 4.386–47 3.244–49
3.042–45 2.864–25 3.062–91
2.945–62 2.762–23 2.996–66
2.912–90 2.955–63
2.853–51
2.763–60
Density, g/cm
3
2.205 (calc) 2.27–2.36 2.18
Optical data
α
1.500 1.501–1.504 1.488
β
1.509 1.505–1.508 1.490
γ
1.515 1.513–1.518 1.493
Optical sign, 2
V
(–)60° (+)57–68° (calc) (+)80°
Source Pekov et al. (2011a) Hesse et al.. 1992; This study
Zubkova et al.2010
Mineraly
(1992)
* As for other minerals in this table, the rhodesite unit cell is given in the setting with Si layers coplanar to the
ab
plane.
rhodesite series to günterblassite as a triplelayered
aluminosilicate (Table 3). It can be supposed that a
further increase in the number of layers will result in
the formation of a 3D framework similar to those of
feldspathoids, scapolites, and zeolites.
Some minerals associated with günterblassite were
altered to some extent. For example, the crystals of
akermanite and götzenite are partially or completely
replaced by Xray amorphous hydrosilicates. The
structural features of günterblassite (disordered large

662
GEOLOGY OF ORE DEPOSITS
Vol. 54
No. 8
2012
CHUKANOV et al.
cations, the sites of which are partially vacant, and
high water content) and the similarity to the del
hayelite–fivegite–hydrodelhayelite evolution series
(Pekov et al., 2011a) indicate that günterblassite is a
transformational mineral species formed as a result of
the hydration and leaching of alkaline cations, Ca, and
probably halogens from a hypothetic primary anhy
drous cationsaturated mineral with the retention of
the initial triplelayered aluminosilicate packet. The
compromise growth surfaces between günterblassite
and nepheline and leucite clearly indicate that the
hypothetic anhydrous protophase of günterblassite
crystallized simultaneously with these minerals. This
protophase was most likely transformed into günter
blassite at the lowtemperature stage simultaneously
with the crystallization of abundant zeolites. The sig
nificant content of barium in günterblassite may be
caused by postcrystallization ion exchange.
ACKNOWLEDGMENTS
This study was supported by the Russian Founda
tion for Basic Research (projects nos. 110512001ofi
m2011, 110500407a, 110591331NNIO_a).
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2–
2