Obsidian rocks forms from molten lava that cooled very quickly and had no time to form into glass. It is said to be a type of volcanic glass, and is found in a number of places worldwide. There are a number of different variations of this stone, and it comes in a range of types and colors. This includes the beautiful rainbow crystals... that may be green and purple, brown, blue and green.
Snowflake Obsidian is the black and white stone, and Apache Tears are also in this family, and have some excellent qualities. It has an excellent spiritual grounding vibration and also has a strong psychic protection energy. The different types of this crystal have different metaphysical properties, but all sorts have excellent healing attributes. Found all over the world, but these are found near Minersville, Utah.