Obsidian is volcanic glass, and it can be very, very sharp! It becomes this way because it cools very rapidly and doesn’t have time to grow crystals. It’s used in many ways, past and present: pottery, art, knives, arrowheads, etc.
Photo by kevinzim on Flickr

Obsidian is volcanic glass, and it can be very, very sharp! It becomes this way because it cools very rapidly and doesn’t have time to grow crystals. It’s used in many ways, past and present: pottery, art, knives, arrowheads, etc.

Photo by kevinzim on Flickr