Gerstmannite
A valid IMA mineral species
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About Gerstmannite
Ewald Gerstmann
Formula:
MnMgZn(SiO4)(OH)2
Colour:
White to very pale pink.
Lustre:
Sub-Adamantine, Vitreous, Silky
Hardness:
4½
Specific Gravity:
3.68
Crystal System:
Orthorhombic
Name:
Named in 1977 by Paul Brian Moore and Takaharu Araki after Mr. Ewald "The Dutchman" Gerstmann [September 19, 1918 in Bremerhaven, Germany - December 14, 2005, Andover, New Jersey], stationary engineer, mineral dealer, and avid collector of Franklin Mining District minerals. Operator of a private mineral museum and collectors' gathering spot at Franklin, NJ, for many years. The Gerstmann mineral collection was donated to the Franklin Mineral Museum.
This page provides mineralogical data about Gerstmannite.
Unique Identifiers
Mindat ID:
1685
Long-form identifier:
mindat:1:1:1685:4
IMA Classification of Gerstmannite
Approved
IMA Formula:
Mn2+MgZn2+SiO4(OH)2
Approval year:
1975
Classification of Gerstmannite
9.AE.25
9 : SILICATES (Germanates)
A : Nesosilicates
E : Nesosilicates with additional anions (O,OH,F,H2O); cations in tetrahedral [4] coordination
9 : SILICATES (Germanates)
A : Nesosilicates
E : Nesosilicates with additional anions (O,OH,F,H2O); cations in tetrahedral [4] coordination
52.2.1.4
52 : NESOSILICATES Insular SiO4 Groups and O,OH,F,H2O
2 : Insular SiO4 Groups and O, OH, F, and H2O with cations in [4] and >[4] coordination
52 : NESOSILICATES Insular SiO4 Groups and O,OH,F,H2O
2 : Insular SiO4 Groups and O, OH, F, and H2O with cations in [4] and >[4] coordination
14.7.21
14 : Silicates not Containing Aluminum
7 : Silicates of Ba, Sr and Zn
14 : Silicates not Containing Aluminum
7 : Silicates of Ba, Sr and Zn
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 |
|---|---|---|
| Gmn | 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 Gerstmannite
Sub-Adamantine, Vitreous, Silky
Transparency:
Translucent, Opaque
Comment:
silky when matted
Colour:
White to very pale pink.
Streak:
White
Hardness:
4½ on Mohs scale
Cleavage:
Distinct/Good
good on {010}
good on {010}
Density:
3.68(2) g/cm3 (Measured) 3.66 g/cm3 (Calculated)
Optical Data of Gerstmannite
Type:
Biaxial (-)
RI values:
nα = 1.655(2) nβ = 1.657(2) nγ = 1.678(2)
2V:
Measured: 50° to 60°, Calculated: 36°
Max. Birefringence:
δ = 0.023
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:
Very High (positive)
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:
weak
Chemistry of Gerstmannite
Mindat Formula:
MnMgZn(SiO4)(OH)2
Element Weights:
Common Impurities:
Fe,Na
Crystallography of Gerstmannite
Crystal System:
Orthorhombic
Class (H-M):
mmm(2/m2/m2/m) - Dipyramidal
Cell Parameters:
a = 8.185(7) Å, b = 18.65(2) Å, c = 6.256(6) Å
Ratio:
a:b:c = 0.439 : 1 : 0.335
Unit Cell V:
954.98 ų (Calculated from Unit Cell)
Z:
8
Comment:
Space Group: Bbcm
Crystal Structure
Load
Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
Show
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Big Balls | Small Balls | Just Balls | Spacefill
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Display Options
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Perspective On | Perspective Off
2D | Stereo | Red-Blue | Red-Cyan
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View
CIF File Best | x | y | z | a | b | c
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Rotation
Stop | Start
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Labels
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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) |
|---|---|---|---|---|---|---|---|
| 0000554 | Gerstmannite | Moore P B, Araki T (1977) Gerstmannite, a new zinc silicate mineral and a novel cubic close-packed oxide structure American Mineralogist 62 51-59 |  | 1977 | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 2.598 Å | (100) |
| 9.326 Å | (85) |
| 3.418 Å | (80) |
| 2.758 Å | (75) |
| 2.332 Å | (75) |
| 2.983 Å | (60) |
| 4.806 Å | (50) |
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| High-? alteration and/or metamorphism | |
| 32 : Ba/Mn/Pb/Zn deposits, including metamorphic deposits |
Type Occurrence of Gerstmannite
Place of Conservation of Type Material:
Harvard University, Cambridge, Massachusetts, 126484; National Museum of Natural History, Washington, D.C., USA, 135926, 137021.
Associated Minerals at Type Locality:
Synonyms of Gerstmannite
Other Language Names for Gerstmannite
Related Minerals - Strunz-mindat Grouping
| 9.AE.05 | Beryllite | Be3(SiO4)(OH)2 · H2O |
| 9.AE.10 | Euclase | BeAl(SiO4)(OH) |
| 9.AE.15 | Sverigeite | NaMnMgSnBe2(SiO4)3(OH) |
| 9.AE.20 | Hodgkinsonite | Mn2+Zn2(SiO4)(OH)2 |
| 9.AE.30 | Clinohedrite | CaZn(SiO4) · H2O |
| 9.AE.35 | Stringhamite | CaCu(SiO4) · H2O |
| 9.AE.40 | Katoptrite | (Mn2+,Mg)13(Al,Fe3+)4Sb5+2(SiO4)2O20 |
| 9.AE.45 | Yeatmanite | Zn6Mn2+9Sb5+2(SiO4)4O12 |
| 9.AE.50 | Sphaerobertrandite | Be3(SiO4)(OH)2 |
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 Gerstmannite
mindat.org URL:
https://www.mindat.org/min-1685.html
Please feel free to link to this page.
Please feel free to link to this page.
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References for Gerstmannite
Localities for Gerstmannite
Showing 1 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.
USA (TL) | |
| Moore et al. (1977) +1 other reference |
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Sterling Mine, Sterling Hill, Ogdensburg, Sussex County, New Jersey, USA