Natural glass such as obsidian forms when ____.
A)magma cools too rapidly for crystals to form
B)pegmatite melts, moves to Earth's surface and ,re-forms
C)magma cools too slowly for crystals to form
D)magma has a very low silica content
E)gas escapes through lava

Question

Quizplus · Accepted Answer

Natural glass such as obsidian forms when magma cools too rapidly for crystals to form, resulting in a solid material without a crystalline structure.

Natural Glass Such as Obsidian Forms When ____