Sentences with phrase «occurring volcanic glass»
Obsidian, naturally occurring volcanic glass, is smooth, hard, and far sharper than a surgical scalpel when fractured, making it a highly desirable raw material for crafting stone tools for almost all of human history.
https://www.sciencedaily.com/ Not exact matches
Last summer, we found small pieces of volcanic glass in a cave that might be from an eruption that occurred in Indonesia nearly 70,000 years ago.