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Quartz is perhaps the most famous mineral family on earth, with several well-known gem materials having also been derived from its various crystalline or microcrystalline forms.

The crystalline quartz gemstones are those occurring as single transparent crystals that are of sufficient size for faceting, with the most famous examples being the purple amethyst, yellow citrine, brownish smoky quartz and colorless rock crystal. In addition, when the latter contains inclusions of visual interest, sub-varieties such as tourmalinated quartz, rutilated quartz and dendritic quartz are named after the identity and/or appearance of these inclusions. White milky quartz and pink rose quartz are also crystalline, but generally, lack the transparency of the above-listed varieties.

Known under the blanket term of chalcedony, the microcrystalline quartzes include carnelian, sard, onyx, chrysoprase and bloodstone, as well as the various agate and jasper sub-varieties such as moss agate, banded agate, picture jasper and brecciated jasper.