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

Chemical composition: CaC0₃, with 56% CaO and 44% C0₂. Fe⁺², Mg⁺² and Mn⁺² replace Ca⁺² to certain extent.

Physical properties:

(i) Form: Commonly crystallised in form of rhombohedron; also occurs in fibrous, lamellar, stalactitic, nodular, granular and compact forms.

(ii) Colour: Colourless or white; sometimes with gray, yellow, blue, red, brown or black tints

(iii) Lustre: Vitreous to earthy.

(iv) Streak: White.

(v) Hardness: 3.

(vi) Cleavage: Perfect 3 sets.

(vii) Fracture: Uneven.

(viii) Specific gravity: 2.71.

(ix) Diaphaneity: Transparent to translucent.

Use: Iceland spar, a transparent variety of calcite is used in the construction of Nicol prism, which is used to produce polarized light in petrological microscopes. Calcite is used as flux in extraction of iron metal from iron ores, in manufacture of quicklime, cement, bleaching powder, calcium carbide, glass, soap, paper, paint etc. It is also used as building and ornamental stones.