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 is a semiconductor, but it seems to vary depending on where it comes from. The material shown here from Tywarnhayle mine near Porthtowan, is unable to carry any current at all and is an insulator. However material from Bassett and Grylls mine near Wendron seems to provide a voltage drop and a mildly asymmetrical response. This second form, although identical in terms of chemistry, is known as specularite as a more reflective form of hematite.