Quartz Crystal

THE major use for quartz crystal is in the manufacture of radio oscillator plates and telephone resonator and filter crystals. Quartz crystal is also cut and polished as a semiprecious gem stone, particularly in the colored varieties (amethyst, Brazilian topaz, and others), and often is carved into various objects of art. Prisms, wedges, lenses and other optical parts often are made of quartz crystal, usually for special- purpose instruments. Chips and small clear crystals below 100 grams in weight, called “lascas” by the trade, are the raw material for fused quartz products. HISTORICAL BACKGROUND The Greeks believed quartz to be permanently frozen water and therefore called it krustallos, which, literally translated, means clear ice; but ages before their civilization, prehistoric man had crudely cut and polished crystals for rough charms and ornaments. About 2000 B.C., the Egyptians brought the art of cutting quartz to a high level. While there are earlier examples of crystal art that have great value, working in crystal during that period became a means of artistic and religious expression that has endured through the ages. Art museums and private collections throughout the world contain many priceless pieces. They include findings from the tombs of the earliest Egyptian rulers, as well as magnificent art objects in both clear and colored crystal encrusted with silver, gold, enamel, and precious gems of oriental and European workmanship. Pierre Curie first measured the piezoelectric effect of quartz, in 188 1, by placing a weight on the surface of a quartz crystal and measuring the resulting electrical charge, which he found was proportional to the weight applied. The following year the inverse piezoelectric effect was proved by the Curies. By applying a voltage to a piece of quartz, a measurable physical displacement occurs. The first practical application of this effect was the construction of a bimorph unit to measure voltage by measuring the amount of the displacement of the end of the bimorph. The piezoelectric properties of quartz crystal remained largely a laboratory curiosity until World War I, when a supersonic device for