Chromatite
A valid IMA mineral species
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About Chromatite
Formula:
CaCr6+O4
Colour:
Yellow, violet
Lustre:
Dull, Earthy
Specific Gravity:
3.142 (Calculated)
Crystal System:
Tetragonal
Name:
Named by F. J. Eckhardt and W. Heimbach in 1963 for the chemical composition.
Type Locality:
Earthy yellow coatings.
Isotypic with zircon and xenotime.
Compare 'UM2011-01-CrO:CaH' - a dihydrate counterpart; and the compositionally similar 'Unnamed (Calcium Chromium Oxide Postspinel)'. Also chemically similar to ellinaite.
Isotypic with zircon and xenotime.
Compare 'UM2011-01-CrO:CaH' - a dihydrate counterpart; and the compositionally similar 'Unnamed (Calcium Chromium Oxide Postspinel)'. Also chemically similar to ellinaite.
Unique Identifiers
Mindat ID:
1030
Long-form identifier:
mindat:1:1:1030:2
Similar Names
| Achromatite | A synonym of 'Achrematite' |
| Chromitite | A rock classification type |
IMA Classification of Chromatite
Approved
Classification of Chromatite
7.FA.10
7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
F : Chromates
A : Without additional anions
7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
F : Chromates
A : Without additional anions
Dana 7th ed.:
35.3.2.1
35.3.2.1
35 : ANHYDROUS CHROMATES
3 : AXO4
35 : ANHYDROUS CHROMATES
3 : AXO4
27.2.3
27 : Sulphites, Chromates, Molybdates and Tungstates
2 : Chromates
27 : Sulphites, Chromates, Molybdates and Tungstates
2 : Chromates
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 |
|---|---|---|
| Crm | IMA–CNMNC | Warr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
Pronunciation of Chromatite
Pronunciation:
| Play | Recorded by | Country |
|---|---|---|
| Jolyon Ralph | United Kingdom |
Physical Properties of Chromatite
Dull, Earthy
Transparency:
Translucent
Comment:
Low luster reported because of the powdery occurrence
Colour:
Yellow, violet
Comment:
Violet crystals (Mo-, Pb-bearing) from Bleiberg, Austria.
Streak:
Yellow
Cleavage:
None Observed
Fracture:
Conchoidal
Density:
3.142 g/cm3 (Calculated)
Optical Data of Chromatite
Type:
Uniaxial (+)
RI values:
nω = 1.81 - 1.85 nε = 1.84 - 1.88
Max. Birefringence:
δ = 0.030
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 uniaxial interference figure - the conoscopic
(convergent-light, Bertrand-lens-in) view, for a grain cut with the optic axis
centred and vertical. The coloured rings are isochromatics, computed with the
same physics as the Michel-Lévy bar above; the dark cross is the isogyre.
For a genuinely uniaxial mineral viewed this way, that cross stays perfectly stationary if you rotate the stage - unlike a biaxial mineral, where it splits apart on rotation. That invariance is itself the standard diagnostic test for telling uniaxial and biaxial minerals apart at the microscope.
For a genuinely uniaxial mineral viewed this way, that cross stays perfectly stationary if you rotate the stage - unlike a biaxial mineral, where it splits apart on rotation. That invariance is itself the standard diagnostic test for telling uniaxial and biaxial minerals apart at the microscope.
Chemistry of Chromatite
Mindat Formula:
CaCr6+O4
Element Weights:
Elements listed:
Crystallography of Chromatite
Crystal System:
Tetragonal
Class (H-M):
4/mmm(4/m2/m2/m) - Ditetragonal Dipyramidal
Space Group:
I41/amd
Cell Parameters:
a = 7.242 Å, c = 6.290 Å
Ratio:
a:c = 1 : 0.869
Unit Cell V:
329.89 ų (Calculated from Unit Cell)
Morphology:
Observed as earthy coating at type locality
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
Remove metal-metal sticks
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
Black Background | White Background
Perspective On | Perspective Off
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
Stop | Start
Labels
Console Off | On | Grey | Yellow
Console Off | On | Grey | Yellow
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) |
|---|---|---|---|---|---|---|---|
| 0017660 | Chromatite | Clouse J (1932) Investigations on the X-Ray Crystal Structures of Ca Cr O4, Ca Cr O4 * H2 O and Ca Cr O4 * (H2 O)2 _cod_database_code 1010939 Zeitschrift fur Kristallographie 83 161-171 |  | 1932 | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 3.62 Å | (100) |
| 2.88 Å | (20) |
| 2.68 Å | (50) |
| 2.56 Å | (10) |
| 2.38 Å | (20) |
| 1.85 Å | (40) |
| 1.81 Å | (20) |
| 1.50 Å | (10) |
Comments:
8-458 synthetic
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| High-? alteration and/or metamorphism | |
| 33 : Minerals deposited by hydrothermal metal-rich fluids (see also [#12]) | |
| Stage 10a: Neoproterozoic oxygenation/terrestrial biosphere | <0.6 |
| 51 : Pyrometamorphic minerals (see also #54 and #56) | <0.36 |
Type Occurrence of Chromatite
General Appearance of Type Material:
Earthy coatings
Geological Setting of Type Material:
In sedimentary rock units at the type location.
Associated Minerals at Type Locality:
Other Language Names for Chromatite
Common Associates
Associations Based on Photo Data:
| 1 photo of Chromatite associated with Halotrichite | Fe2+Al2(SO4)4 · 22H2O |
Related Minerals - Strunz-mindat Grouping
| 7.FA.05 | Tarapacáite | K2(CrO4) |
| 7.FA.15 | Hashemite | BaCr6+O4 |
| 7.FA.20 | Crocoite | PbCr6+O4 |
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 Chromatite
mindat.org URL:
https://www.mindat.org/min-1030.html
Please feel free to link to this page.
Please feel free to link to this page.
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External Links:
Mineral Dealers:
References for Chromatite
Localities for Chromatite
Showing 10 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 | |
| Puttner (1997) |
Greece | |
| Tsoupas et al. (2021) |
Israel | |
| Gross (1977) |
Jordan | |
| Sokol +9 other references |
Middle East | |
| Gross (1977) | |
Norway | |
| Piilonen et al. (2012) +1 other reference |
Palestine | |
| Sokol et al. (2011) |
| Naturwiss. (1963) +1 other reference |
Russia | |
| Kozlov et al. (2011) |
South Africa | |
| McDonald et al. (1995) +1 other reference |
Quick NavTopAbout ChromatiteUnique IdentifiersSimilar NamesIMA Classification Classification Mineral SymbolsPronunciation Physical Properties Optical Data Chemistry Crystallography Crystal StructureX-Ray Powder DiffractionGeological EnvironmentType Occurrence Other LanguagesCommon AssociatesStrunz-MindatOther InformationInternet Links References Localities Locality List
Ma'ale Adumim, Quds Governorate, West Bank, Palestine