Crocoite
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Description
A bright red mineral composed of Lead chromate. Crocoite has been found in Tasmania (Dundas), Ural Mountains, Romania, Brazil, the Philippines and the United States (Arizona). Although the rare mineral has the same composition as Chrome yellow, it was not ground for use as a pigment. The element chromium was, however, discovered in this mineral in 1787. About 1820, after the development of commercial production of chromium, chrome yellow was produced synthetically.
Physical and Chemical Properties
- Monoclinic system with prismatic crystals.
- Cleavage is distinct in one direction.
- Fracture = conchoidal.
- Luster = adamantine to vitreous.
- Streak = orange-red.
| Composition | PbCrO4 |
|---|---|
| Mohs Hardness | 2.5 - 3.0 |
| Density | 5.9-6.1 g/ml |