Economic Minerals Questions and Answers

Answer: B

Cassiterite is the main ore mineral of tin.

Cassiterite is tin dioxide, SnO₂, and almost all the world's tin comes from it, either from veins and greisens around granites or from placer deposits, as in South-East Asia. In India it occurs in the Bastar region of Chhattisgarh.

Tungsten comes from wolframite and scheelite, titanium from ilmenite and rutile, and tantalum from tantalite (columbite-tantalite). None of them is obtained from cassiterite.

Answer: A

Diamonds are explored in kimberlites and lamproites.

Diamond forms at depths of more than about 150 km in the mantle. It reaches the surface only in magmas that rise very quickly from those depths, chiefly kimberlite and lamproite, which erupt through ancient cratons as pipes. The Argyle mine in Australia is in lamproite; most South African and Indian primary deposits, such as Majhgawan in Madhya Pradesh, are kimberlite or related pipes.

Komatiites are ultramafic lavas known for nickel sulphides, not diamonds. Spilites are sodium-altered submarine basalts, and anorthosites are plagioclase-rich plutonic rocks; neither comes from diamond depths.

Answer: A

The PGE ore mineral is sperrylite.

Sperrylite is platinum arsenide, PtAs₂, and is one of the most important platinum minerals, mined for example at Sudbury and in the Bushveld Complex.

The others contain no platinum group elements. Digenite (Cu₉S₅) and bornite (Cu₅FeS₄) are copper sulphides and are ores of copper. Diopside, CaMgSi₂O₆, is a calcium-magnesium clinopyroxene, a rock-forming silicate and not an ore mineral at all.

Answer: C

Polymetallic nodules contain significant amounts of Cu-Ni-Co.

Manganese nodules on the abyssal plains, such as the Clarion-Clipperton zone of the Pacific and the Central Indian Ocean Basin where India holds an exploration contract, are mostly manganese and iron oxides. Their economic interest lies in the copper, nickel and cobalt they carry, together typically around 2 to 3 percent, along with the manganese itself.

Uranium, thorium and niobium; lead, zinc and titanium; and mercury, molybdenum and platinum are not the characteristic metals of the nodules, though some occur in traces.