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Jasper is an opaque stone originating from silica rich sediment or volcanic ash. It can occur in any color depending on the mineral content of the original sediment. Beautiful patterns can also occur in jasper. This happens when the original rock- forming materials are fractured or distorted in the ground, and then are later filled in with other minerals. A specific jasper may be named for its location, or may be named imaginatively by describing its unique appearance.
Obsidian is a type of naturally occurring volcanic glass, produced when lava cools rapidly with minimal crystal growth. It has a high silica content, and upon rapid cooling, it results in a natural glass. The brittle quality of Obsidian lends itself to be sharpened, just as shards of glass are extremely sharp. For this reason, Obsidian has been used to make cutting and piercing tools, such as arrowheads and experimentally as surgical blades.
