Hematite
From cornish semiconductor corporation
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- Lustre:Metallic, Sub-Metallic, Dull, Earthy
- Transparency:Opaque
- Colour:Steel-grey to black in crystals and massively crystalline ores, dull to bright "rust-red" in earthy, compact, fine-grained material.
- Streak:Reddish brown ("rust-red"); blackish when Ti-bearing
- Hardness:5 - 6 on Mohs scale
- Tenacity:Brittle
- Cleavage:None Observed
- Parting:Partings on {0001} and {1011} due to twinning. Unique cubic parting in masses and grains at Franklin Mine, Franklin, NJ.
- Fracture:Irregular/Uneven, Sub-Conchoidal
Hematite is an iron ore, and very common in the earths crust - but not that usual to find good crystallised forms of it in Cornish copper and tin mines.
Hematite apparently is a semiconductor, but trying the specimen shown here I found at Tywarnhayle mine near Porthtowan, similar to wolframite it was unable to carry any current at all. Specularite is a different form of hematite, which I will also test.