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AMETHYST

Click on the image to see a larger version copyright statement	Description: Dark brown amethyst, 3[SiO2], coated with green chrysocolla, CuSi2O3.2H2O; over that, a layer of drusy quartz with sparse crystal bundles of deep green malachite, 4[Cu2CO3(OH)2].
	Locality: Guerrero, Mexico
	Photo donor: Image is by courtesy of Stuart Wilensky www.wilenskyminerals.com