Macrocrystalline: Rock Crystal, Blue Quartz, Smoky Quartz

These quartz varieties are macrocrystalline; they are made up of crystals visible to the unaided eye. This appearance may take the form of a large, single crystal, or a mass of crystallites with no visible faces. The differences in color are caused by traces of other minerals locked into the crystal structure. These impurities make up about 0.5% of a specimen’s composition, but can affect its color such that it may be mistaken for a different mineral at a glance.

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