A naturally occurring volcanic glass, Obsidian is created when lava rich in the elements that form feldspar and quartz cools rapidly and experiences minimal crystal growth. It has a high silica content which results in a rock that, while hard, is also brittle. When it fractures, it leaves extremely sharp edges. In the past, it has been formed into blades and arrowheads, while more recently it has found experimental use as surgical scalpel blades. It can be sharpened to approximately 3 nanometers thick, and when viewed beneath an electron microscope is still smooth. By comparison, the sharpest metal knife has a jagged and irregular blade when viewed beneath a strong microscope.
Obsidian is typically dark in appearance with slight color variations depending on the presence of impurities. With the inclusion, or trapping, of white, radially clustered crystals of cristobalite within the gas bubbles that were present within the obsidian when it cooled, the black glass acquires a blotchy, snowflake-style pattern from where Snowflake Obsidian takes its name. Each piece measures approximately 1.25 x 1.25 inches.
