Rob Lavinsky, iRocks.com – CC-BY-SA-3.0 [CC-BY-SA-3.0], via Wikimedia Commons
Chromite is shiny and black, and makes a curious-looking cabochon with no special attraction. Occasionally, a cabochon has a reddish color. The stones have little value because the material is extremely abundant but are cut as curiosities only.
| Data | Value |
|---|---|
| Name | Chromite |
| Is a Variety of | Spinel |
| Crystallography | Isometric. Octahedral crystals up to 1 cm on edge; massive. |
| Refractive Index | 2.08-2.16 |
| Colors | Black, reddish brown. |
| Hardness | 5.5 |
| Fracture | Uneven |
| Cleavage | None |
| Luminescence | None |
| Luminescence Present | No |
| Absorption Spectrum | Not diagnostic. |
| Formula | FeCr2 O4 |
| Pleochroism | None. |
| Optics | RI = 2.08-2.16. Isotropic. |
| Luster | Submetallic. |
| Specific Gravity | 4.5-4.8 |
| Transparency | Opaque, translucent in thin splinters. |
| Birefringence | None |
Chromite group, extensive solid-solution series.
Note: Magnesiochromite = MgCr2 O4; Hercynite = FeAl2O4.
Optics: R.I. = 2.08-2.16. Isotropic.
Occurrence: in igneous rocks rich in olivine; in serpentines; in stream and beach sands. Sometimes in massive deposits of large size.
California; Oregon; Washington; Wyoming; Maryland; North Carolina; Pennsylvania.
Canada; Cuba; Norway; USSR; France; Zimbabwe; India.
Stone Sizes: Any size could be cut from massive material. The possibility exists for some deep reddish crystals to contain very tiny facetable areas, but thus far none have been discovered.
Comments: Chromite is shiny and black, and makes a curious-looking cabochon with no special attraction. Occasionally, a cabochon has a reddish color. The stones have little value because the material is extremely abundant but are cut as curiosities only.
Sometimes weakly magnetic.
Name: In allusion to the composition.
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