Amstallite
A valid IMA mineral species
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About Amstallite
Formula:
CaAl[(Al,Si)4O8(OH)2](OH)2 · (H2O,Cl)
Colour:
Colourless
Lustre:
Vitreous
Hardness:
3 - 5
Specific Gravity:
2.40
Crystal System:
Monoclinic
Name:
Named after the type locality at Amstall, Lower Austria, Austria.
Unique Identifiers
Mindat ID:
208
Long-form identifier:
mindat:1:1:208:6
IMA Classification of Amstallite
Approved
IMA Formula:
CaAl(Si,Al)4O8(OH)4·(H2O,Cl)
Approval year:
1986
First published:
1987
Classification of Amstallite
9.DP.25
9 : SILICATES (Germanates)
D : Inosilicates
P : Transitional ino-phyllosilicate structures
9 : SILICATES (Germanates)
D : Inosilicates
P : Transitional ino-phyllosilicate structures
72.1.4.1
72 : PHYLLOSILICATES Two-Dimensional Infinite Sheets with Other Than Six-Membered Rings
1 : Two-Dimensional Infinite Sheets with Other Than Six-Membered Rings with 4-membered rings
72 : PHYLLOSILICATES Two-Dimensional Infinite Sheets with Other Than Six-Membered Rings
1 : Two-Dimensional Infinite Sheets with Other Than Six-Membered Rings with 4-membered rings
16.9.32
16 : Silicates Containing Aluminum and other Metals
9 : Aluminosilicates of Ca
16 : Silicates Containing Aluminum and other Metals
9 : Aluminosilicates of Ca
Mineral Symbols
As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.
| Symbol | Source | Reference for Standard |
|---|---|---|
| Ams | IMA–CNMNC | Warr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
Physical Properties of Amstallite
Vitreous
Transparency:
Transparent, Translucent
Colour:
Colourless
Hardness:
3 - 5 on Mohs scale
Tenacity:
Brittle
Cleavage:
Distinct/Good
good on {100}
good on {100}
Fracture:
Conchoidal
Density:
2.40(5) g/cm3 (Measured) 2.38 g/cm3 (Calculated)
Optical Data of Amstallite
Type:
Biaxial (+)
RI values:
nα = 1.533 nβ = 1.534 nγ = 1.538
2V:
Measured: 57° to 59°, Calculated: 54°
Max. Birefringence:
δ = 0.005
Based on recorded range of RI values above.
Based on recorded range of RI values above.
Interference Colours:
The colours simulate birefringence patterns seen in thin section under crossed polars. They do not take into account mineral colouration or opacity.
Michel-Levy Bar The default colours simulate the birefringence range for a 30 µm thin-section thickness. Adjust the slider to simulate a different thickness.
Grain Simulation You can rotate the grain simulation to show how this range might look as you rotated a sample under crossed polars. Each grain retains its interference colour (retardation) while its brightness falls to black at extinction and reaches a maximum between extinction positions.
The colours simulate birefringence patterns seen in thin section under crossed polars. They do not take into account mineral colouration or opacity.
Michel-Levy Bar The default colours simulate the birefringence range for a 30 µm thin-section thickness. Adjust the slider to simulate a different thickness.
Grain Simulation You can rotate the grain simulation to show how this range might look as you rotated a sample under crossed polars. Each grain retains its interference colour (retardation) while its brightness falls to black at extinction and reaches a maximum between extinction positions.
Surface Relief:
None to Very Low
Relative to Canada balsam mounting medium (n ≈ 1.537).
Relative to Canada balsam mounting medium (n ≈ 1.537).
This shows the grain boundary and Becke line effect under plane-polarised
light, based on the contrast between this mineral's average refractive
index and the mounting medium. It does not take into account mineral
colouration.
In focus
Interference Figure:
This shows the idealized biaxial acute bisectrix (Bxa) interference figure
- the conoscopic view for a grain cut perpendicular to the acute bisectrix, using
this mineral's 2V. The two small white dots mark the melatopes - the points
where the two optic axes emerge - and are shown only when they fall within the
field of view. The coloured bands are isochromatics, and the dark bands are
isogyres.
Rotate the stage: at 0°/90° the isogyres form a cross through the melatopes; at 45° they pull apart into curved hyperbolas. That splitting on rotation - absent in a uniaxial figure - is the standard diagnostic test for telling biaxial minerals from uniaxial ones. If 2V is large, the melatopes may fall outside the field of view, as they often do at the microscope too.
Rotate the stage: at 0°/90° the isogyres form a cross through the melatopes; at 45° they pull apart into curved hyperbolas. That splitting on rotation - absent in a uniaxial figure - is the standard diagnostic test for telling biaxial minerals from uniaxial ones. If 2V is large, the melatopes may fall outside the field of view, as they often do at the microscope too.
Dispersion:
r > v weak
Chemistry of Amstallite
Mindat Formula:
CaAl[(Al,Si)4O8(OH)2](OH)2 · (H2O,Cl)
Element Weights:
Crystallography of Amstallite
Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
B2/b
Setting:
C2/c
Cell Parameters:
a = 18.83 Å, b = 11.51 Å, c = 5.19 Å
β = 100.86°
β = 100.86°
Ratio:
a:b:c = 1.636 : 1 : 0.451
Unit Cell V:
1,104.70 ų (Calculated from Unit Cell)
Z:
4
Morphology:
As acicular prismatic crystals, to 1 cm, elongated and commonly striated parallel to [001], with cross sections appearing rhombohedral or hexagonal.
Crystal Structure
Load
Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
Show
Big Balls | Small Balls | Just Balls | Spacefill
Polyhedra Off | Si Polyhedra | All Polyhedra
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Big Balls | Small Balls | Just Balls | Spacefill
Polyhedra Off | Si Polyhedra | All Polyhedra
Remove metal-metal sticks
Display Options
Black Background | White Background
Perspective On | Perspective Off
2D | Stereo | Red-Blue | Red-Cyan
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2D | Stereo | Red-Blue | Red-Cyan
View
CIF File Best | x | y | z | a | b | c
CIF File Best | x | y | z | a | b | c
Rotation
Stop | Start
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Labels
Console Off | On | Grey | Yellow
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Data courtesy of the American Mineralogist Crystal Structure Database. Click on an AMCSD ID to view structure
| ID | Species | Reference | Link | Year | Locality | Pressure (GPa) | Temp (K) |
|---|---|---|---|---|---|---|---|
| 0014815 | Amstallite | Quint R (1987) Description and crystal structure of amstallite, CaAl(OH)2[Al0.8Si3.2O8(OH)2]*[(H2O)0.8Cl0.2], a new mineral from Amstall, Austria Neues Jahrbuch fur Mineralogie, Monatshefte 1987 253-262 | 1987 | Amstall, Austria | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 9.75 Å | (100) |
| 5.43 Å | (70) |
| 4.714 Å | (60) |
| 4.069 Å | (40) |
| 3.816 Å | (90) |
| 3.603 Å | (100) |
| 3.175 Å | (60) |
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Stage 5: Initiation of plate tectonics | <3.5-2.5 |
| 40 : Regional metamorphism (greenschist, amphibolite, granulite facies) |
Type Occurrence of Amstallite
Place of Conservation of Type Material:
Natural History Museum Vienna, Vienna, Austria: 1) Holotype (recognised as such in Nov. 2025; cat. no. O 3987; formerly in the collection of the Institut für Mineralogie, Kristallographie and Strukturchemie of the Technical University Vienna, Vienna, Austria, cat. no. 5248); 2) Cotype (cat. no. M 455).
Note that the original description did not give any cat. no.(s).
(Updated on Nov. 28, 2025 by Uwe Kolitsch, Curator at the Natural History Museum Vienna.)
Note that the original description did not give any cat. no.(s).
(Updated on Nov. 28, 2025 by Uwe Kolitsch, Curator at the Natural History Museum Vienna.)
Geological Setting of Type Material:
In open fissures cutting pegmatitic schlieren, in hydrothermally altered graphite-bearing metamorphic rocks.
Associated Minerals at Type Locality:
Synonyms of Amstallite
Other Language Names for Amstallite
Dutch:Amstalliet
French:Amstallite
German:Amstallit
Norwegian:Amstallitt
Russian:Амсталлит
Spanish:Amstallita
Common Associates
Associations Based on Photo Data:
Related Minerals - Strunz-mindat Grouping
| 9.DP.05 | Meliphanite | (Ca,Na)2(Be,Al)[Si2O6(OH,F)] |
| 9.DP.15 | Leucosphenite | BaNa4Ti2B2Si10O30 |
| 9.DP.20 | Ferriprehnite | Ca2Fe3+(Si3AlO10)(OH)2 |
| 9.DP.20 | Prehnite | Ca2Al2Si3O10(OH)2 |
| 9.DP.30 | Kvanefjeldite | Na4(Ca,Mn)(Si3O7)2(OH)2 |
| 9.DP.35 | Lemoynite | (Na,K)2CaZr2Si10O26 · 5H2O |
| 9.DP.35 | Hogarthite | (Na,K)2CaTi2Si10O26 · 8H2O |
| 9.DP.35 | Natrolemoynite | Na4Zr2Si10O26 · 9H2O |
| 9.DP.40 | Altisite | Na3K6Ti2Al2Si8O26Cl3 |
| 9.DP.45 | Chiappinoite-(Y) | Y2Mn(Si3O7)4 |
| 9.DP.50 | Esquireite | BaSi6O13 · 7H2O |
| 9.DP.55 | Lavinskyite | K(LiCu)Cu6(Si4O11)2(OH)4 |
| 9.DP.55 | Plancheite | Cu8(Si8O22)(OH)4 · H2O |
Other Information
Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.
Internet Links for Amstallite
mindat.org URL:
https://www.mindat.org/min-208.html
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Please feel free to link to this page.
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References for Amstallite
Localities for Amstallite
Showing 2 localities.
symbol to view information about a locality.
The Locality List
- This locality has map coordinates listed.
- This locality has estimated coordinates.
ⓘ - Click for references and further information on this occurrence.
? - Indicates mineral may be doubtful at this locality.
- Good crystals or important locality for species.
- World class for species or very significant.
(TL) - Type Locality for a valid mineral species.
(FRL) - First Recorded Locality for everything else (eg varieties).
All localities listed without proper references should be considered as questionable.
Austria (TL) | |
| Quint (1987) |
Jordan | |
| Dill et al. (2009) |
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Graphite quarry, Amstall, Mühldorf, Krems-Land District, Lower Austria, Austria