Obsidian is a naturally occurring volcanic glass formed in igneous rock. It is produced when lava flowing from a volcano cools rapidly. Obsidian is hard with very sharp edges, which were used in the past in cutting and piercing tools. Small, white, clustered crystals of cristobalite in the black glass produce snowflake pattern (snowflake obsidian). The approximate stone size is 2.5cm – 3cm. Believed to have positive health benefits, these gemstones can be used for a variety of purposes.