Silicate Mineral Groups Questions and Answers

Answer: C

Feldspar is \(\mathrm{KAlSi_{3}O_{8}}\).

KAlSi₃O₈ is potassium feldspar (orthoclase or microcline). The feldspars are framework aluminosilicates of potassium, sodium and calcium and are the most abundant mineral group in the Earth's crust; albite (NaAlSi₃O₈) and anorthite (CaAl₂Si₂O₈) complete the family.

SiO₂ is quartz, Al₂O₃ is corundum (alumina), and Al₂SiO₄(OH)₂ is the formula of topaz with hydroxyl in place of fluorine. None of them contains the potassium that identifies feldspar here.

Answer: B

Asbestos is a family of naturally occurring silicon-based minerals.

Asbestos is a commercial name for six fibrous silicate minerals: chrysotile (white asbestos) of the serpentine group, and five amphiboles, including crocidolite (blue) and amosite (brown). Their fibres resist heat, which made them popular in building materials, but inhaled fibres cause asbestosis, lung cancer and mesothelioma.

They are silicates, not carbon-based minerals. Selenium and tellurium are unrelated elements and do not form asbestos.

Answer: D

The barium mineral is Celsian.

Celsian is the barium feldspar, BaAl₂Si₂O₈, the barium analogue of anorthite. It occurs in manganese and barium-rich metamorphic rocks and is named after Anders Celsius.

The others contain no barium: corundum is aluminium oxide (Al₂O₃), apatite is calcium phosphate with fluorine, chlorine or hydroxyl, and gypsum is hydrated calcium sulphate. The common barium mineral barite (BaSO₄) is not among the options.

Answer: B

The anthophyllite-cummingtonite series belongs to the inosilicates.

Anthophyllite (orthorhombic) and cummingtonite (monoclinic, spelt 'Commingtonite' in the paper) are magnesium-iron amphiboles. Amphiboles are double-chain silicates, built from chains of SiO₄ tetrahedra linked in pairs; single-chain pyroxenes and double-chain amphiboles together form the inosilicate (chain silicate) subclass.

Cyclosilicates have rings of tetrahedra (beryl, tourmaline). Sorosilicates have pairs of tetrahedra (epidote). Phyllosilicates have sheets (micas, clays).