Obsidian is an igneous rock, formed when lava cools very quickly, which disallows the formation of any crystalline structures. Vitreous, it is a glass-like rock which takes several forms depending upon the minerals in the base. It is extremely durable and known for keeping an immaculate and sharp edge, excellent for surgery or fine work. The rock is not a mineral, but has many qualities that make it desirable for jewelry; color, sheen, durability, and availability. It is sometimes classified as a “mineraloid.”
Valued for arrowheads and blades, the rocks were traded widely by Native Americans and other indigenous peoples, so they can be found all over the world, not necessarily where they were found.
Black Obsidian –This is like a solid black glass, found all over the world, but in the USA, only west of the Mississippi, at sites of later volcanic activity. Central Oregon is known for its extrusive lava flows and the formation of obsidian. This is the most common color of obsidian, colored by iron, with the composition consisting of mostly granite and rhyolite.
Mahogany Obsidian-This rock is formed when swirls of black and brown are mixed, often appearing brownish-red with more iron. It is highly used by jewelers, and yet possesses the same qualities of holding an excellent edge for blades as the black obsidian.
Rainbow Obsidian-This iridescent obsidian seems to hold all the colors of the rainbow- it can be found in Mexico, California and Oregon. The rock actually holds trace minerals which have the colors in their composition. It has also been called “golden” or “silver” obsidian, depending upon the sheen of the colors. This type is highly prized by jewelry-makers.
Fire Obsidian-This rare obsidian is a result of many thin, isolated layers of clear rock which refract light into changing vibrant and unique colors. These specimens have been by Cal-Tech as actually having thin crystallized layers of magnetite.
Snowflake or Apache Tears Obsidian-The white and grey markings of snowflake obsidian are striking, resembling snowflakes or flowers. This rock is mainly found in Wyoming and Utah, with a black, opaque background. Native Americans called this the “Book of Laws” stone and Aztecs called it the “divine stone”, so many varied and complicated spiritual associations go with this one. The snowflakes are actually part of the aging process in an unstable rock, when crystals are beginning to form, after a few million years.
Obsidian is a durable and versatile rock, easily surface-mined, and recognizable. The varieties of obsidian retain the same attributes in common and are quite affordable as semi-precious stones.