Quartz

Quartz is one of the most common minerals in the Earth’s crust. As a mineral name, quartz refers to a specific chemical compound (silicon dioxide, or silica, SiO2), having a specific crystalline form (hexagonal). It is found is all forms of rock: igneous, metamorphic and sedimentary. Quartz is physically and chemically resistant to weathering. When quartz-bearing rocks become weathered and eroded, the grains of resistant quartz are concentrated in the soil, in rivers, and on beaches. The white sands typically found in river beds and on beaches are usually composed mainly of quartz, with some white or pink feldspar as well.

Type

Mineral

Mineral Classification

Silicate

Chemical Formula

SiO2

Streak

White

Moh's Hardness

7

Crystal System

trigonal

Color

Pure quartz is clear. Color variance due to impurities: purple (amethyst), white (milky quartz), black (smoky quartz), pink (rose quartz) and yellow or orange (citrine)

Luster

vitreous, waxy, dull

Fracture

conchoidal

Description

Quartz is one of the most common minerals in the Earth’s crust. As a mineral name, quartz refers to a specific chemical compound (silicon dioxide, or silica, SiO2), having a specific crystalline form (hexagonal). It is found is all forms of rock: igneous, metamorphic and sedimentary. Quartz is physically and chemically resistant to weathering. When quartz-bearing rocks become weathered and eroded, the grains of resistant quartz are concentrated in the soil, in rivers, and on beaches. The white sands typically found in river beds and on beaches are usually composed mainly of quartz, with some white or pink feldspar as well.

Relation to Mining

Quartz crystal is found in many countries and many geologic environments. Major producers of natural quartz crystals are the United States (particularly Arkansas) and Brazil. Natural quartz is rarely used as found in nature (especially in electrical applications), except as a gemstone. Natural quartz crystals have too many chemical impurities and physical flaws. As a result, a commercial process of manufacturing pure, flawless, electronics-grade quartz was developed. “Cultured quartz,” that is, quartz crystals grown very carefully in highly controlled laboratory conditions, is the quartz that is used in industry. About 200 metric tons of cultured quartz is produced each year. In the production of cultured quartz crystals, a “seed crystal” is needed. A seed crystal is a small piece of carefully selected, non-electronics-grade quartz. The manufactured crystal grows on this seed crystal.

Uses

Quartz crystal is one of several minerals which are piezoelectric, meaning that when pressure is applied to quartz, a positive electrical charge is created at one end of the crystal and a negative electrical charge is created at the other. These properties make quartz valuable in electronics applications. Electronics-grade manufactured quartz is used in a large number of circuits for consumer electronics products such as computers, cell phones, televisions, radios, electronic games, etc. It is also used to make frequency control devices and electronic filters that remove defined electromagnetic frequencies.