[Chemistry Class Notes] on Quartz Pdf for Exam

Quartz is a widely distributed mineral of several varieties that primarily consists of silicon dioxide (SiO2) or silica. Minor impurities such as sodium, lithium, titanium, and potassium can be present. This mineral has attracted more attention from the earliest times; ancient Greeks know water-clear crystals as krystallos. Thus, the name crystal, or more generally rock crystal, is applied to this variety. The term quartz is an old German word of uncertain origin, which was first used by Georgius Agricola in 1530.

Importance of Quartz

Quartz contains greater economic importance. Several varieties are given as gemstones, including citrine, amethyst, rose quartz, and smoky quartz. Sandstone, which is composed majorly of quartz, is an essential building stone. Huge amounts of quartz sand (which is also called silica sand) are used in the manufacture of ceramics and glass for foundry molds in metal casting. Crushed quartz can be used as an abrasive in silica, sandpaper, and it is employed in sandblasting. Still, sandstone is used as a whole to make millstones, grindstones, and whetstones. Silica glass (which is also known as fused quartz) can be used in optics to transmit ultraviolet light. Tubing and other different vessels of fused quartz have more important laboratory applications, and quartz fibres can be employed in extremely sensitive weighing devices.

Quartz is given as the second most abundant mineral in the crust of the Earth after feldspar. It takes place in approximately all metamorphic, sedimentary and acid igneous rocks. It is an important mineral in such silica-rich felsic rocks as granodiorites, rhyolites, and granites. It is highly resistant to weathering and also tends to concentrate in sandstones, including other detrital rocks. On the other side, secondary quartz serves as a cement in the sedimentary rocks of this type by forming the overgrowths on detrital grains. Microcrystalline varieties of silica such as flint, chert, jasper, and agate consist of a fine quartz network. Typically, metamorphism of the quartz-bearing sedimentary and igneous rocks increases the quartz amount and its grain size.

Etymology

The term “quartz” has derived from the German term named “Quarz,” which had a similar form in the first half of the 14th century in East Central German and the Middle of High German and which came from the Polish dialect word “kwardy,” that corresponds to the Czech word tvrdý (“hard”).

Existence of Quartz

The element of quartz exists in two forms. Let us discuss the types of quartz or quartz types and meanings.

(1) alpha-, or the low, quartz – It is stable up to the temperature of 573 °C (1,063 °F),

(2) beta-, or the high quartz – It is stable above the temperature of 573 °C.

These two are closely related, only with small movements of their constituent atoms at the alpha-beta transition. The beta-quartz structure is hexagonal, either with left- or right-handed symmetry groups, which are equally populated in crystals. The alpha-quartz structure is trigonal, again either with a right-handed or left-handed symmetry group. Whereas, at the transition temperature, the beta-quartz’s tetrahedral framework twists, which is resulting in the symmetry of alpha-quartz; the atoms move from special space group positions to the more general positions.

At temperatures more than 867 °C (1,593 °F), the beta-quartz changes into tridymite, but the transformation is slower because the bond breaking occurs to form a more open structure. At very high pressure, the alpha-quartz transforms into the coesite and still, at higher pressures, as stishovite. Such types of phases have been observed in the impact craters.

Quartz Production

Quartz is also defined as piezoelectric, which is a crystal that develops both positive and negative charges on an alternate prism edge when it is subjected to either tension or pressure. These charges are proportional to the same change in pressure. Due to its piezoelectric property, a quartz plate is used as a pressure gauge, as in the apparatus of depth-sounding.

Just as tension and compression form opposite charges, the converse effect is, alternating opposite charges will cause the alternating contraction and expansion. A section that cuts from a quartz crystal with the definite dimensions and orientation contains a natural frequency of this contraction and expansion (that is, vibration) that is very high, which is measured in millions of vibrations per one second. The quartz, which is the properly cut plates, can be used for the frequency control in televisions, radios, including other electronic communications equipment, and also for crystal-controlled watches and clocks.

Japan, Russia, and China are given as the world’s major and primary quartz producers. Brazil, Belgium, France, Bulgaria, South Africa, the United Kingdom, and Germany also mine significant amounts of this mineral.

Synthetic and Artificial Treatment

Not all quartz varieties are naturally occurring. A few clear quartz crystals are also treated using gamma or heat irradiation to induce the colour where it would not otherwise occur naturally. Susceptibility to such treatments will depend on the location where the quartz was mined.

Prasiolite, which is an olive-coloured material, can be produced by the heat treatment; natural prasiolite has also been observed in the Lower Silesia in Poland. Although the citrine takes place naturally, the majority is given as the result of smoky or heat-treating amethyst quartz. To deepen its colour, carnelian is widely heat-treated.