Kyanite,andalusite,and sillimanite ____.
A) are index minerals formed from clay-rich parent rocks
B) form from the same parent rocks under different combinations of pressure and temperature
C) can transform from one to the other depending on changes in temperature and pressure
D) have the same chemical composition
E) all of these

Question

Quizplus · Accepted Answer

Kyanite, andalusite, and sillimanite are polymorphs, meaning they have the same chemical composition (Al2SiO5) but different crystal structures. They form from the same parent rocks under different conditions of pressure and temperature, and they can transform from one to another depending on these conditions. Thus, all the statements are correct.

Kyanite,andalusite,and Sillimanite ____