|
Name Origin | In allusion to the composition |
---|---|
Chemical Formula | ZnO + Mn |
Color | Dark red, brownish red, deep yellow, orange-yellow; colorless if pure |
Occurrence |
In metamorphosed limestone and zinc ores |
Hardness | 4 - 4.5 on Mohs Scale |
Crystal System | Hexagonal. Crystals hemimorphic and very scarce; massive, cleavable, compact, grains. |
Cleavage | Perfect 1 direction but difficult. Fracture conchoidal |
Specific Gravity (SG) | 5.68 |
Luster | subadamantine to adamantine |
Stone size |
Cabochons have been cut from granular zincite in white calcite from Franklin. Faceted gems of Franklin material are very rare, maximum 20 carats. Most of the few faceted zincites are in the 1-3 carat range |
Streak |
orange-yellow |
Pleochroism | None |
Note: Zincite is a very rare mineral, essentially restricted to one important locality. Well-terminated crystals were found only up to about 3-4 inches, but larger masses, weighing several pounds, have been encountered in the ore bodies. These are not especially interesting, but cabochons with red zincite, green willemite, and white calcite, peppered with black franklinite, are unique to the Franklin occurrence and are extremely beautiful as well as highly fluorescent. Spheres have also been cut from this material. Cut zincite is one of the rarest of all gemstones
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