Obsidian is an extrusive igneous rock. They get their black glassy texture by rapid cooling of silica-rich lava.Its composition is extremely felsic. Its major minerals include feldspar, quartz, and mica. Today, Obsidian can be used in making surgical scalpels. Obsidian is also used as jewelry of course. Since it can scratch easily and is likely to chip upon impact, it is mostly used for earrings, brooches, and pendants. its hardness is set at 5.5. Obsidian is most commonly found is the United States, Mexico, Canada, Argentina, Kenya, Italy, Greece, and Iceland.
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