Chemical composition: CuFeS2, small amount of Ag, Au and Zn may be present in the lattice.

Physical properties:

(i) Form: Crystalline and massive aggregates.

(ii) Colour: Brass-yellow

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(iii) Lustre: Metallic.

(iv) Streak: Greenish black.

(v) Hardness: 3-4.

(vi) Cleavage: Imperfect.

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(vii) Fracture: Conchoidal to uneven.

(viii) Specific gravity: 4.1 – 4.3.

(ix) Diaphaneity: Opaque.

Use: Chief ore of copper.

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Gypsum

Chemical composition: CaS04-2H20;. Minor amounts of Fe, Mn, Cr may be present.

Physical properties:

(i) Form: Crystalline, laminated, granular, fibrous (Satin spar) and fine-grained massive (Alabaster).

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(ii) Colour: Colourless (Selenite), white, gray, various shades of yellow, red, brown.

(iii) Lustre: Vitreous, pearly and silky.

(iv) Streak: White.

(v) Hardness: 2 can be scratched by finger nail.

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(vi) Cleavage: Perfect one set.

(vii) Fracture: Conchoidal.

(viii) Specific gravity: 2.32.

(ix) Diaphaneity: Transparent to translucent, (ix) Tenacity: Sectile

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Use:

Production of plaster of Paris and making of adamant plaster for interior use. Gypsum serves as a soil conditioner and land plaster for fertilizer. Uncalcined gypsum is used as a retarder in Portland cement. Satin spar and alabaster are cut and polished for ornamental purposes. It is also used in manufacture of gypsum plate used in petrological microscopes.