Hematite

General

 

Category: Oxide minerals

 

Chemical formula: iron(III) oxide, Fe2O3, α-Fe2O3

 

Strunz classification: 04.CB.05

 

Crystal symmetry: Trigonal hexagonal scalenohedral H-M symbol: (32/m) Space group: R3c

 

Unit cell: a = 5.038(2) Å, c = 13.772(12) Å; Z = 6

 

 

Identification

 

Color: Metallic gray, dull to bright red

 

Crystal habit: Tabular to thick crystals; micaceous or platy, commonly in rosettes; radiating fibrous, reniform, botryoidal or stalactitic masses, columnar; earthy, granular, oolitic

 

Crystal system: Trigonal

 

Twinning: Penetration and lamellar

 

Cleavage: None, may show partings on {0001} and {1011}

 

Fracture: Uneven to sub-conchoidal

 

Tenacity: Brittle

 

Mohs scale hardness: 5.5–6.5

 

Luster: Metallic to splendent

 

Streak: Bright red to dark red

 

Diaphaneity: Opaque

 

Specific gravity: 5.26

 

Optical properties: Uniaxial (-)

 

Refractive index: nω = 3.150–3.220, nε = 2.870–2.940

 

Birefringence: δ = 0.280

 

Pleochroism: O = brownish red; E = yellowish red

 

Done