Hematite: A primary ore of iron and a pigment mineral
Mohs Hardness: 5 to 6.5: Specific Gravity: 5.0 to 5.3: Diagnostic Properties: Red streak, specific gravity: Chemical Composition: Fe 2 O 3: Crystal System: Trigonal: ... The crushed coal, which has a very low specific gravity, is placed on the heavy liquid and the light clean coal floats, while high-specific-gravity impurities such as pyrite sink.
