For the time being I am finished talking about obsidian. For my final obsidian post I would like to answer a question that some may be wondering: is obsidian a rock or a mineral?
To be honest I’m not exactly sure. To be classified as a mineral a substance must be an in-organic, naturally occurring, homogenous solid that has a definite chemical composition and a crystal structure. A rock is a natural aggregation (mixture) of minerals. Generally a rock is a mixture of more than one mineral, but sometimes it is composed of only one such as marble, which is made entirely of calcite. Obsidian is an inorganic homogenous solid, but it has no crystal structure and an indefinite chemical formula. One piece that I read described obsidian as a mineraloid, which is a mineral-like substance that does not have a crystal structure, and is of an indefinite chemical composition. This very same piece, however, also described obsidian as an igneous rock, a label that obsidian is also able to wear as it is a mixture of minerals. Most other books that I’ve read seem to call obsidian a rock, but it is still a difficult call to make.
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