garnet

garnet, name applied to a group of isomorphic minerals crystallizing in the cubic system. They are used chiefly as gems and as abrasives (as in garnet paper). The garnets are double silicates; one of the metallic elements is calcium, magnesium, ferrous iron, or manganese and the other aluminum, ferric iron, or chromium. Six varieties (of which there are also intermediate forms) are distinguished according to composition—grossularite (calcium-aluminum), pyrope (magnesium-aluminum), spessartite (manganese-aluminum), almandite (iron-aluminum), andradite (calcium-iron), and uvarovite (calcium-chromium). Grossularite occurs commonly in a red, green, yellow, or brown shade, depending on the impurities; if pure it would be colorless. The yellow and brown stones, coming chiefly from Sri Lanka, are used as gems under the names essonite (or hessonite) and cinnamon stone; sometimes they are miscalled hyacinth. Grossularite is found also in the Transvaal, in Mexico, and in Oregon. The most popular variety of garnet is the ruby-red pyrope from Bohemia, S Africa, and Arizona, sold as Cape ruby and Arizona ruby. Rhodolite, a mixture of pyrope and almandite from North Carolina, is rose-red or purple. Spessartite, a brown to brownish-red garnet from Bavaria, Sri Lanka, and parts of the United States, is seldom used for jewelry. Deep red, transparent almandite is the carbuncle; it was formerly a very popular gem. Almandites come chiefly from Brazil, India, and Sri Lanka; Australia and parts of the United States are also important sources. Andradite, a very common variety, is usually some shade of red, black, brown, yellow, or green. Gem varieties include topazolite, similar in color and transparency to topaz; demantoid, a green variety with a high dispersion and adamantine luster, sometimes miscalled olivine and Uralian emerald; and black melanite. Demantoid is found in the Urals, and the other andradites come chiefly from Europe and the United States. Uvarovite, an emerald-green variety from Russia and Finland, is rarely suitable for gem use. Garnet occurs in many different kinds of rocks—grossularite, in metamorphosed impure limestones; pyrope, in basic igneous rocks; spessartite, in granite rocks; almandite, in schists and other metamorphic rocks as well as in igneous rocks; andradite, in serpentine; and uvarovite, chiefly in serpentine.

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garnet

Any of a group of common silicate minerals with identical crystal structure but highly variable chemical composition. Garnets are most often found in metamorphic rocks but also occur in certain types of igneous rocks, and, usually in minor amounts, in some sedimentary rocks. They may be colourless, black, or many shades of red and green. Garnets are hard, and they fracture with sharp edges. They are used as abrasives for fine sanding and polishing of wood, leather, glass, metals, and plastics, as sandblasting agents, and in nonskid surface coatings. Garnet is the birthstone for January. Garnets have been mined in New York, Maine, and Idaho in the U.S., the world's leading producer; notable quantities have also been found in Australia, China, India, and elsewhere.

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garnet

January. [Am. Gem Symbolism: Kunz, 319–320]

See : Birthstones

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1.		Garnet - A graphical object editor and Macintosh environment.
2.		Garnet - A user interface development environment for Common Lisp and X11 from The Garnet project team. It helps you create graphical, interactive user interfaces. Version 2.2 includes the following: a custom object-oriented programming system which uses a prototype-instance model. automatic constraint maintenance allowing properties of objects to depend on properties of other objects and be automatically re-evaluated when the other objects change. The constraints can be arbitrary Lisp expressions. Built-in, high-level input event handling. Support for gesture recognition. Widgets for multi-font, multi-line, mouse-driven text editing. Optional automatic layout of application data into lists, tables, trees or graphs. Automatic generation of PostScript for printing. Support for large-scale applications and data visualisation. Also supplied are: two complete widget sets, one with a Motif look and feel implemented in Lisp and one with a custom look and feel. Interactive design tools for creating parts of the interface without writing code: Gilt interface builder for creating dialog boxes. Lapidary interactive tool for creating new widgets and for drawing application-specific objects. C32 spreadsheet system for specifying complex constraints. Not yet available: Jade automatic dialog box creation system. Marquise interactive tool for specifying behaviours. ftp://a.gp.cs.cmu.edu/usr/garnet/garnet.