4.6" Polished Snowflake Obsidian Section - Utah

Snowflake obsidian is found near Sevier Lake in Millard County, Utah. It is a natural, volcanic "glass" that is formed when molten rock cools so quickly that that atoms do not have enough time to arrange themselves into crystals. Instead, the molten material solidifies into an amorphous solid called a glass.
The "snowflakes" in the obsidian are small, white, radially clustered crystals of cristobalite, a mineral polymorph of silica.

Obsidian was important material for many ancient people. It was used for making tools, weapons, jewelry and decorative items. It was a major barter material for Native Americans. When broken its conchoidal fracturing results in extremely sharp edges which made it ideal for making knives, scrapers, arrowheads and spearpoints. It is even occasionally used today to produce surgeons scalpels as the edges are several times sharper (only 3 nanometers) than blades that can be produced from steel.