Rock Forming Minerals Questions and Answers

Answer: C

Correct answer: the assertion is false although the reason offered is a true statement in itself

The reason is true and irrelevant: the scale does run from 1 to 10, but it is an ordinal scale, recording only which mineral scratches which. The intervals are not equal and are wildly unequal at the top - diamond at 10 is several times harder than corundum at 9, while the step from 4 to 5 is small. A Mohs number cannot be used in a proportion.

Answer: D

Quartz is chemically resistant and its framework offers no easy attack, whereas feldspar hydrolyses readily. The residual soil is therefore quartz grains in a clay matrix, which is the commonest soil profile over granite.

Answer: A

Correct answer: its flakes cleave easily and bond poorly to cement

Mica’s perfect basal cleavage makes each flake a plane of weakness, and its flat faces bond poorly to the cement paste while raising the water demand. Those are the reasons a micaceous aggregate is rejected. Mica is not dense, does not effervesce and is not magnetic, so none of the other three describes it at all.