Quartz is the most common material identified as the mystical substance
maban in
Australian Aboriginal mythology. It is found regularly in passage tomb cemeteries in Europe in a burial context, such as
Newgrange or
Carrowmore in
Ireland. Quartz was also used in
prehistoric Ireland, as well as many other countries, for
stone tools; both vein quartz and rock crystal were
knapped as part of the
lithic technology of prehistoric peoples. While
jade has been the most prized semi-precious stone for carving in
East Asia and
pre-Columbian America since earliest times, in Europe and the Middle East different varieties of quartz were the most commonly used for the various types of
jewelry and
hardstone carving, including
engraved gems and
cameo gems,
rock crystal vases, and extravagant vessels. The tradition continued to produce highly valued objects until the mid-19th century, when it largely fell from fashion except in jewelry. Cameo technique exploits the bands of color in onyx and other varieties. Efforts to synthesize quartz began in the mid-19th century as scientists attempted to create minerals under laboratory conditions that mimicked the conditions in which the minerals formed in nature. German geologist
Karl Emil von Schafhäutl (1803–1890) was the first person to synthesize quartz when in 1845 he created microscopic quartz crystals in a
pressure cooker. However, the quality and size of the crystals that were produced by these early efforts were poor. Elemental impurity incorporation strongly influences the ability to process and utilize quartz. Naturally occurring quartz crystals of extremely high purity, necessary for the crucibles and other equipment used for growing perfect large
silicon boules to be sliced into silicon
wafers in the
semiconductor industry, are expensive and rare. These
high-purity quartz are defined as containing less than 50 ppm of impurity elements. A major mining location for
high-purity quartz is the
Spruce Pine Mining District in
Spruce Pine, North Carolina, United States. Quartz may also be found in
Caldoveiro Peak in
Asturias, Spain. By the 1930s, the electronics industry had become dependent on quartz crystals. The only source of suitable crystals was Brazil; however,
World War II disrupted supplies from Brazil, so nations attempted to synthesize quartz on a commercial scale. German mineralogist Richard Nacken (1884–1971) achieved some success during the 1930s and 1940s. After the war, many laboratories attempted to grow large quartz crystals. In the United States, the U.S. Army Signal Corps contracted with
Bell Laboratories and with the
Brush Development Company of Cleveland, Ohio to synthesize crystals following Nacken's lead. (Prior to World War II, Brush Development produced piezoelectric crystals for record players.) By 1948, Brush Development had grown crystals that were 1.5 inches (3.8 cm) in diameter, the largest at that time. By the 1950s,
hydrothermal synthesis techniques were producing synthetic quartz crystals on an industrial scale, and today virtually all the quartz crystal used in the modern electronics industry is synthetic.
George Washington Pierce designed and patented
quartz crystal oscillators in 1923. The
quartz clock is a familiar device using the mineral; it is simply a clock that uses a quartz oscillator as its time reference. Warren Marrison created the first quartz oscillator clock based on the work of Cady and Pierce in 1927. The resonant frequency of a quartz crystal oscillator is changed by mechanically loading it, and this principle is used for very accurate measurements of very small mass changes in the
quartz crystal microbalance and in
thin-film thickness monitors. File:Milan Jug with cut festoon decoration.jpg|Rock crystal jug with cut festoon decoration by a
Milan workshop from the second half of the 16th century,
National Museum,
Warsaw. Milan, apart from
Prague and
Florence, was the main
Renaissance centre for crystal cutting. File:Prototype synthetic quartz autoclave 1959.jpg|Synthetic quartz crystals produced in the autoclave shown in
Western Electric's pilot hydrothermal quartz plant in 1959 File:Ewer birds Louvre MR333.jpg|
Fatimid ewer in carved rock crystal (clear quartz) with gold lid, Almost all the industrial demand for quartz crystal (used primarily in electronics) is met with synthetic quartz produced by the hydrothermal process. However, synthetic crystals are less prized for use as gemstones. The popularity of
crystal healing has increased the demand for natural quartz crystals, which are now often mined in
developing countries using primitive mining methods, sometimes involving
child labor. == See also ==