Snowflake Obsidian

Obsidian is a rock which is a type of naturally occurring glass, produced by volcanoes (igneous origin) when a felsic lava cools rapidly and freezes without sufficient time for crystal growth. It is commonly found within the margins of felsic lava flows, where cooling is more rapid. Because of the lack of crystal structure, obsidian blade edges can reach almost molecular thinness, leading to its ancient use as arrowheads and its modern use as surgical scalpel blades.

While a rock like basalt is dark because of ferromagnesian enrichment, obsidian consists mainly of silicon dioxide, usually 70% or more. Obsidian is mineral-like, but not a true mineral because it is not crystalline. Its composition is very similar to that of granite and rhyolite. It is sometimes classified as a Mineraloid because obsidian is metastable at the earth's surface (over time the glass becomes fine-grained mineral crystals). The breakdown of obsidian is accelerated by the presence of water. Tektites were once thought by many to be obsidian produced by lunar volcanic eruptions, though few scientists now agree with this theory.

While pure obsidian is always dark in appearance, the color varies depending on the presence of impurities. Iron and magnesium typically give the obsidian a dark green to brown to black color. In some stones, the inclusion of small, white, radially clustered crystals of Cristobalite in the black glass develop a blotchy or snowflake pattern producing what is known as