Mineral Class: Glass (Not a true mineral)
Crystal System: Amorphous
Hardness: 5 - 6
Colors: Black, White, Brown, Red
Source: Worldwide (including Canada, Chile, Greece, Iceland, Italy, Japan, Mexico, New Zealand, Peru, Russia and USA)
Obsidian is a naturally occurring volcanic glass formed as an extrusive igneous rock. Obsidian is created when lava extruded from a volcano cools rapidly with minimal crystal growth. It is commonly found in obsidian flows. The inhibition of atomic diffusion through this highly viscous and polymerized lava explains the lack of crystal growth. Obsidian is hard and brittle and fractures with incredibly sharp edges. Although Obsidian is mineral-like, it is not a true mineral because as a glass it is not crystalline.
There are many different forms of Obsidian, such as Black, Rainbow, Snowflake, Velvet, Mahogany, and Gold Sheen. An interesting feature of Obsidian is the way in which it breaks. It is known as a conchoidal fracture which is when it breaks into pieces with curved surfaces that are razor thin and extremely sharp. Ancient Aztecs used flat sheets of Obsidian as mirrors and ancient peoples created arrowheads and axes.