What are the physical properties of obsidian?
Obsidian is a type of igneous rock that cools instantly after a volcano explosion. Obsidian forms when lava enters the water directly after the volcano erupts. The water instantly cools the lava leaving the mineral crystals no time grow. The microscopic minerals give obsidian a glassy feel and look. Obsidian can be brown, black, or black and white. Obsidian can often be found in the shape of arrow heads because it was used as a primitive arrow.
