|Rock Class||igneous rock|
|Volcanic (volcanic glass)|
Medium: 3.00-4.00 cm
Large: 4.00-5.00 cm
Obsidian, or volcanic glass, is molten lava that has cooled rapidly. Its composition is mainly of silicic oxides, being very similar to that of granite or rhyolite.
The piece you receive may differ slightly from the photo shown as the rocks are natural and no piece is identical. The size is approximate.