Hematite - WikipediaHematite, also spelled as haematite, is the mineral form of iron(III) oxide (Fe2O3), one of several iron oxides. It is the oldest known iron oxide mineral and is widespread in rocks and soils. Hematite crystallizes in the rhombohedral lattice system, and it has the same crystal structure as ilmenite and corundum. Hematite and.elemental composition of hematite in iron ore,Hematite: A primary ore of iron and a pigment mineral - GeologyCleavage, None. Mohs Hardness, 5 to 6.5. Specific Gravity, 5.0 to 5.3. Diagnostic Properties, Red streak, specific gravity. Chemical Composition, Fe2O3. Crystal System, Trigonal. Uses, The most important ore of iron. Pigment, heavy media separation, radiation shielding, ballast, polishing compounds, a minor gemstone.