Although muscovite, feldspar and quartz are not considered useful as index minerals, which of the following situations could be useful in determining the grade of metamorphism in a region?
A) the coexistence of muscovite, feldspar and quartz
B) the disappearance of rocks containing muscovite and quartz
C) the coexistence of feldspar and quartz
D) the disappearance of rocks containing quartz

Question

Quizplus · Accepted Answer

The disappearance of rocks containing muscovite and quartz can indicate higher-grade metamorphism, as these minerals break down or transform at higher temperatures and pressures.

Although Muscovite, Feldspar and Quartz Are Not Considered Useful as Index