Minerals Topics

Major Mineral Groups (Part 6)

Silicates (continued)

Quartz Pronounce:

• Quartz, a very common mineral, has a composition of SiO2.

Chert and Quartz

Quartz is made up of silicon and oxygen.  This very common mineral occurs as clear to gray crystals in igneous and metamorphic rocks.  It is also abundant as reworked grains in sediment and sedimentary rocks. (Photographs by Parvinder Sethi)

• Quartz is identified by its hexagonal crystal form; glassy luster; conchoidal fracture; and color variations.

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• Its hardness is 7.

• Its specific gravity is 2.65.

• Quartz is used in abrasives, glass, and gemstones.

• Quartz varieties include amethyst, rose quartz, milky quartz, smoky quartz, onyx, jasper, chert, flint, agate, and citrine.

Quartz ColorsQuartz occurs in many different varieties.  Rose quartz, smoky quartz (black or gray), amethyst (purple), and clear quartz are some of the examples of color variation in quartz. (Photographs by Parvinder Sethi)