Commodity Code
obsidian
http://resource.geosciml.org/classifier/cgi/commodity-code/obsidian
| definition | Obsidian is the result of volcanic lava coming in contact with water. Often the lava pours into a lake or ocean and is cooled quickly. This process produces a glassy texture in the resulting rock. Iron and magnesium give the obsidian a dark green to black color. Obsidian has been used by ancient people as a cutting tool, for weapons, and for ceremonial purposes and is sometimes found by archaeologists in excavations. |  |
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| source | http://www.galleries.com/Obsidian | |
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| in scheme | commodity code | |||||
| is primary topic of | obsidian | |||||