Snowflake obsidian is also known as flowering obsidian, probably because of the radiating patterns it displays.
Usually black or dark gray with light gray patches, these semiprecious beads, donuts, and pendants are believed to assist with clarity and logic. As with other obsidian beads, snowflake obsidian beads are cut from a naturally-occurring form of glass created by volcanic activity. The gemstone is made from the same minerals as granite, but the minerals cool so quickly when exposed to air that they don't have time to crystallize.
Over a long period of time, obsidian can gradually change from glass to rock. This is known as "devitrification." The silica molecules in the volcanic glass slowly rearrange into organized crystal patterns such as the "snowflakes" of quartz crystals that are found in snowflake obsidian.