People then discovered how to skillfully break the obsidian to produce cutting tools in a variety of shapes.

The first use of obsidian by people probably occurred when a sharp piece of obsidian was used as a cutting These sharp fragments may have prompted the first use of obsidian by people. The conchoidal fracture of obsidian causes it to break into pieces with curved surfaces. The best way to learn about rocks is to have specimens available for testing and examination. Rock & Mineral Kits: Get a rock, mineral, or fossil kit to learn more about Earth materials. Image copyright iStockphoto / Charles Butzin. Obsidian spear point: A spear point fashioned from opaque black obsidian. The mostĬommon color combination is black and brown obsidian swirled together - that's called 'mahogany obsidian' (see photo). Occasionally two colors of obsidian will be swirled together in a single specimen. The colors are thought to be caused mainly by trace elements or inclusions.

However, it can also be brown, tan, or green. Rainbow Obsidian: A baroque cabochon of iridescent 'rainbow obsidian.'īlack is the most common color of obsidian. Mahogany obsidian: A tumble-polished specimen of 'mahogany obsidian.' Image copyright iStockphoto / Arpad Benedek. The nice photo above is from the Glass Butte Rockhounding Site page on the Deschutes National Forest website. Clockwise from upper left are: double flow obsidian, rainbow obsidian, black obsidian, pumpkin obsidian, mahogany obsidian, gold sheen obsidian, and the piece in the center is gold sheen. It shows the diversity of obsidian types that can be found in a small geographic area. Types of Obsidian: The specimens shown above are from Glass Butte rockhounding site in central Oregon.

Mahogany obsidian gemstone