Extrusive Rocks

Physical Characteristics/What Is It Made Of

Obsidian has jagged edges, but is very dark in color and has a glossy look and feel to it. It doesn't have very many crystals formed inside. Obsidian is made up of felsic lava, which made the rock cool very quickly

How And Where Is It Formed/What Is The Rock Used For

Obsidian is usually formed on the outside of a volcano, as soon as the rock is shot out of the volcano it is cooled almost instantly. Sometimes Obsidian is used to make knives, arrows, and scrapers.