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Quartz Clocks
The Shortt clock was replaced as the standard by quartz crystal clocks in the 1930s and 1940s. Quartz clock operation is based on a property of quartz crystals. If you apply an electric…quartz
(Encyclopedia) quartz, one of the commonest of all rock-forming minerals and one of the most important constituents of the earth's crust. Chemically, it is silicon dioxide, SiO2. It occurs in…quartzite
(Encyclopedia) quartzite, usually metamorphic rock composed of firmly cemented quartz grains. Most often it is white, light gray, yellowish, or light brown, but is sometimes colored blue, green,…rock crystal
(Encyclopedia) rock crystal: see quartz.jasper, type of quartz
(Encyclopedia) jasper, opaque, impure cryptocrystalline quartz, usually red, but also yellow, green, and grayish blue. It is used as a gem. Ribbon jasper has the colors in stripes.amethyst
(Encyclopedia) amethystamethystămˈəthĭst [key] [Gr.,=non-drunkenness], variety of quartz, violet to purple in color, used as a gem. It is the most highly valued of the semiprecious quartzes. It is…enamelware
(Encyclopedia) enamelware, utensils having a metal foundation and a coating of special glass, called porcelain enamel, applied by fusion. The porcelain enamel, or vitreous enamel, is applied to make…cat's-eye
(Encyclopedia) cat's-eye, gemstone that displays a thin band of reflected light on its surface when cut as a cabochon. Its name is derived from its supposed resemblance to the eye of a cat. The…sandstone
(Encyclopedia) sandstone, sedimentary rock formed by the cementing together of grains of sand. The usual cementing material in sandstone is calcium carbonate, iron oxides, or silica, and the hardness…onyx
(Encyclopedia) onyxonyxŏnˈĭks [key], variety of cryptocrystalline quartz, differing from agate only in that the bands of which it is composed are parallel and regular. Its appearance is most striking…Trending
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