Question

Basalts are composed of the following minerals

i. Olivine

ii. Pyroxene

iii. Quartz

iv. Plagioclase

Choose the correct answer from the options given below

• A. i, ii and iii only
• B. i, ii and iv only
• C. i, iii and iv only
• D. ii, iii and iv only

Answer 1

Answer:

B. i, ii and iv only

• Mafic Composition: Basalt is a mafic igneous rock, which means it is rich in iron and magnesium but low in silica.

• Core Mineralogy: Its primary mineral constituents are plagioclase feldspar and pyroxene. Many basalts also contain significant amounts of olivine as an accessory mineral or phenocrysts.

• Quartz Exclusion: Quartz is a felsic mineral composed of pure silica. Because basaltic magma is chemically silica-undersaturated, quartz is fundamentally absent (or only present as an incredibly rare trace contaminant) in typical basalts.