Hematite
Fe₂O₃ · Trigonal · also called specularite, kidney ore, bloodstone ore
Hematite is iron oxide and the reason so much of the world's soil and sandstone is red. A shiny black specimen and a dull red one can both be hematite, and the streak plate is what proves it: rub either on unglazed porcelain and you get the same rusty red line.
Properties
- Mohs hardness
- 5–6.5
- Streak
- red brown
- Lustre
- metallic, dull, submetallic
- Colour
- Ranges from mirror-bright silver-black (specular hematite) to dull brick red (earthy hematite). The two look nothing alike, but both give the same red streak.
- Cleavage
- No true cleavage; may show parting.
- Fracture
- Uneven to subconchoidal
- Specific gravity
- 5.2–5.3 (water = 1)
- Magnetism
- Weakly magnetic
- Acid test
- No reaction
- UV
- Not fluorescent
Tests that confirm hematite
- Red-brown streak regardless of the specimen's outward colour. This is the single most reliable test in amateur mineralogy.
- Botryoidal (kidney-shaped) masses are common and distinctive.
- Heavy for a non-metallic-looking rock.
What hematite gets confused with
Each of these is settled by one test. Run that test first.
Magnetite is strongly magnetic with a black streak; hematite is not, and streaks red-brown.
Goethite streaks yellow-brown rather than red-brown.
Where it is found
Banded iron formations, weathered iron-bearing rock, and as the cement in red sandstone. Extremely widespread.
Is it worth anything?
Common and cheap. Polished hematite jewellery is usually 'hematine', a synthetic magnetic substitute — real hematite is not strongly magnetic.