Caswellsilverite
A valid IMA mineral species
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About Caswellsilverite
Caswell Silver
Formula:
NaCrS2
Colour:
Yellowish-grey, Grey
Lustre:
Metallic
Hardness:
2
Specific Gravity:
3.23 (Calculated)
Crystal System:
Trigonal
Name:
Named by Akihiko Okada and Klaus Keil in 1982 in honor of Caswell Silver (25 June 1916, New York City, New York, USA – 18 October 1988), geologist and President of the Sundance Oil Company from 1960-1984. He was an alumnus and benefactor of the Department of Geology and Institute of Meteoritics at the University of New Mexico.
Type Locality:
This page provides mineralogical data about Caswellsilverite.
Unique Identifiers
Mindat ID:
918
Long-form identifier:
mindat:1:1:918:6
IMA Classification of Caswellsilverite
Approved
IMA Formula:
NaCr3+S2-2
Approval year:
1981
First published:
1982
Classification of Caswellsilverite
2.FB.05
2 : SULFIDES and SULFOSALTS (sulfides, selenides, tellurides; arsenides, antimonides, bismuthides; sulfarsenites, sulfantimonites, sulfbismuthites, etc.)
F : Sulfides of arsenic, alkalies; sulfides with halide, oxide, hydroxide, H2O
B : With alkalies (without Cl, etc.)
2 : SULFIDES and SULFOSALTS (sulfides, selenides, tellurides; arsenides, antimonides, bismuthides; sulfarsenites, sulfantimonites, sulfbismuthites, etc.)
F : Sulfides of arsenic, alkalies; sulfides with halide, oxide, hydroxide, H2O
B : With alkalies (without Cl, etc.)
2.9.17.1
2 : SULFIDES
9 : AmBnXp, with (m+n):p = 1:1
2 : SULFIDES
9 : AmBnXp, with (m+n):p = 1:1
3.8.2
3 : Sulphides, Selenides, Tellurides, Arsenides and Bismuthides (except the arsenides, antimonides and bismuthides of Cu, Ag and Au, which are included in Section 1)
8 : Sulphides etc. of Cr, Mo, W an Mn
3 : Sulphides, Selenides, Tellurides, Arsenides and Bismuthides (except the arsenides, antimonides and bismuthides of Cu, Ag and Au, which are included in Section 1)
8 : Sulphides etc. of Cr, Mo, W an Mn
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 |
|---|---|---|
| Cws | 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 Caswellsilverite
Metallic
Transparency:
Opaque
Colour:
Yellowish-grey, Grey
Hardness:
2 on Mohs scale
Hardness:
VHN15=17 - 45 kg/mm2 - Vickers
Comment:
Vickers hardness on synthetic material
Density:
3.23 g/cm3 (Calculated)
Optical Data of Caswellsilverite
Anisotropism:
Strong
Bireflectance:
Strong
Reflectivity:
| Wavelength | R1 (%) | R2 (%) |
|---|---|---|
| 400nm | 19.3% | 26.7% |
| 420nm | 20.1% | 26.2% |
| 440nm | 21.9% | 26.3% |
| 460nm | 21.5% | 27.4% |
| 480nm | 21.7% | 30.0% |
| 500nm | 22.0% | 31.6% |
| 520nm | 22.0% | 32.3% |
| 540nm | 21.8% | 32.8% |
| 560nm | 21.7% | 33.0% |
| 580nm | 21.3% | 32.5% |
| 600nm | 20.8% | 32.2% |
| 620nm | 20.5% | 31.4% |
| 640nm | 20.5% | 30.7% |
| 660nm | 20.1% | 29.4% |
| 680nm | 18.1% | 26.7% |
| 700nm | 18.0% | 28.8% |
Graph shows reflectance levels at different wavelengths (in nm). Peak reflectance is 33.0%.
R1 shown in black, R2 shown in red
Colour in reflected light:
Yellow-gray to light gray
Pleochroism:
Visible
Comments:
Pale yellow to gray in air, pale yellow with greenish tint to gray in oil.
Chemistry of Caswellsilverite
Mindat Formula:
NaCrS2
Element Weights:
Elements listed:
Common Impurities:
Fe,Ca,Mg,Mn,Ti
Crystallography of Caswellsilverite
Crystal System:
Trigonal
Class (H-M):
3m(32/m) - Hexagonal Scalenohedral
Space Group:
R3m
Setting:
R3m
Cell Parameters:
a = 3.54 Å, c = 19.35 Å
Ratio:
a:c = 1 : 5.466
Unit Cell V:
210.00 ų (Calculated from Unit Cell)
Z:
3
Morphology:
Anhedral grains to 1mm
Twinning:
Lamellar twinning (may be result of pressure induce deformation)
Crystal Structure
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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) |
|---|---|---|---|---|---|---|---|
| 0013301 | Caswellsilverite | Engelsman F M R, Wiegers G A, Jellinek F, VanLaar B (1973) Crystal structures and magnetic structures of some metal chromium(III) sulfides and selenides Journal of Solid State Chemistry 6 574-582 | 1973 | synthetic | 0 | 293 | |
| 0013300 | Caswellsilverite | Engelsman F M R, Wiegers G A, Jellinek F, VanLaar B (1973) Crystal structures and magnetic structures of some metal chromium(III) sulfides and selenides Journal of Solid State Chemistry 6 574-582 | 1973 | synthetic | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 2.60 Å | (100) |
| 2.07 Å | (80) |
| 1.910 Å | (80) |
| 1.779 Å | (80) |
| 6.49 Å | (70) |
| 1.465 Å | (60) |
| 1.134 Å | (60) |
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Stage 1: Primary nebular phases | 4.567-4.561 |
| 4 : Primary chondrule phases | 4.566–4.561 |
| Stage 2: Planetesimal differentiation and alteration | 4.566-4.550 |
| 5 : Primary asteroid phases | 4.566–4.560 |
Geological Setting:
Meteorites
Type Occurrence of Caswellsilverite
General Appearance of Type Material:
Opaque inclusions within enstatite crystals as well as in the brecciated matrix of the meteorite.
Place of Conservation of Type Material:
n.d.
Geological Setting of Type Material:
Enstatite achondrite
Associated Minerals at Type Locality:
Synonyms of Caswellsilverite
Other Language Names for Caswellsilverite
Dutch:Caswellsilveriet
German:Caswellsilverit
Russian:Касуэллсилверит
Simplified Chinese:硫钠铬矿
Spanish:Caswellsilverita
Traditional Chinese:硫鈉鉻礦
Related Minerals - Strunz-mindat Grouping
| 2.FB.05 | Schöllhornite | Na0.3CrS2 · H2O |
| 2.FB.05 | Cronusite | Ca0.2CrS2 · 2 H2O |
| 2.FB.10 | Chvilevaite | Na(Cu,Fe,Zn)2S4 |
| 2.FB.15 | Orickite | 2CuFeS2 · H2O |
| 2.FB.20 | Rasvumite | KFe2S3 |
| 2.FB.20 | Pautovite | CsFe2S3 |
| 2.FB.25 | Colimaite | K3VS4 |
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 Caswellsilverite
mindat.org URL:
https://www.mindat.org/min-918.html
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References for Caswellsilverite
Reference List:
Engelsman, F.M.R., Wiegers, G.A., Jellinek, F., Van Laar, B. (1973) Crystal structures and magnetic structures of some metal(I) chromium(III) sulfides and selenides. Journal of Solid State Chemistry, 6. 574-582 doi:10.1016/s0022-4596(73)80018-0
Localities for Caswellsilverite
Showing 9 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.
Africa | |
| Piani et al. (2016) |
Antarctica | |
| Brearley et al. (1998) |
China | |
| Mineralogical Society of America - ... |
India | |
| Nehru et al. (1984) |
Israel | |
| Galuskin et al. (2023) +1 other reference |
| Galuskin et al. (2025) |
Northwest Africa Meteorites | |
| Bunch et al. (2008) | |
USA (TL) | |
| Okada et al. (1982) +1 other reference |
| Fahey et al. (1995) |
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Norton County meteorite, Norton County, Kansas, USA