Week 25: Obsidian

What kind of rock is this?

How have people used it in the past?



Answers:

What kind of rock is this?

This is obsidian, a type of volcanic glass. Obsidian is a black mineral which is formed when lava with the right mineral content cools very quickly. Because it is formed during volcanic activity, it has been found in many areas around the world.

How have people used it in the past?

Because obsidian is very brittle, it forms extremely sharp edges when it breaks. This has led to many cultures using obsidian to make knives or other tools for cutting. Obsidian is also very reflective, making it perfect for use as a mirror. The Aztecs used obsidian mirrors to make prophecies in uncertain times.



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