Short notes on the Chemical composition, Physical properties and uses of Hematite

Chemical composition: Hematite is composed of iron and oxygen. In the purest form it is ferric oxide (Fe₂0₃; Fe = 70% and O = 30%). However, minor amounts of Ti, Fe⁺², A1 and Mn replace Fe⁺³.

Physical properties:

(i) Form: Tabular, micaceous (specularite), foliaceous aggregates, reniform, granular, amorphous (ocher), pseudo-octahedral (martite). Crystallized varieties are rhombohedral.

(ii) Colour: Steel gray to iron black; earthy forms (ocher) are red.

(iii) Lustre: Crystallised varieties (specularite) are metallic and highly splendent, fibrous varieties are silky and amorphous varieties (ocher) are dull and earthy.

(iv) Streak: Cherry red.

(v) Hardness: 5-7.

(vi) Cleavage: Absent.

(vii) Fracture: Subconchoidal.

(viii) Specific gravity: 4.9 – 5.3.

(ix) Diaphaneity: Opaque

(x) Magnetic property: Moderately magnetic

Use:

Used in steel industry for extraction of iron metal and in ferroalloy industries. Red ochre is used as pigment and polishing powder.