Answer:
b. noncrystalline
Explanation:
Volcanic glass -
It is a noncrystalline or amorphous substance , which is formed via rapid cooling of the magma . It is matrix or interstitial .
Volcanic rock is also called as the vitreous igneous rocks .
Most commonly called the obsidian , it is a high silica content , rhyotic glass .
Some example of volcanic glass are , Apache tears , Pumice etc .
