Quarz

Quarz is a mineral composed of silicon dioxide (SiO2). It occurs in many varieties, but the most common form is macrocrystalline quartz, which forms hexagonal crystals that commonly appear as six‑sided prisms with pyramidal terminations. At temperatures below about 573°C it exists as alpha-quartz; above that temperature it becomes beta-quartz, a higher‑temperature polymorph, though the transformation is typically suppressed in nature by pressure and impurities. Quarz is known for its hardness, conchoidal fracture, and vitreous luster. It is usually colorless or translucent, but trace impurities produce a wide range of colors including amethyst, citrine, rose quartz, and smoky quartz.

Quarz has a widespread distribution in Earth's crust, where it makes up a large fraction of many rocks and is the second most abundant mineral after the feldspars. It forms in igneous rocks such as granites and rhyolites, in metamorphic rocks like quartzite, and as cementing material in some sedimentary rocks. It also forms in hydrothermal veins and as geodes in volcanic and sedimentary rocks.

Its physical properties and chemical stability give Quarz numerous commercial applications. Silica sand, a major component of glass and ceramics, is largely quartz. High‑purity Quarz is essential for optical components, laboratory glassware, and microelectronics; fused quartz is used for crucibles and specialized optics. In electronics, quartz crystals exploit the piezoelectric effect to provide stable frequency standards for watches, clocks, radios, and sensors.