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AMETHYST

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Originally appearing in Volume V01, Page 852 of the 1911 Encyclopedia Britannica.
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AMETHYST , a See also:

violet or See also:purple variety of See also:quartz used as an ornamental See also:stone. The name is generally said to be derived from the Gr. a, " not," and µe9iQxew, " to intoxicate," expressing the old belief that the stone protected its owner from strong drink. It was held that See also:wine drunk out of a See also:cup of amethyst would not intoxicate. According, however, to the Rev. C. W. See also:King, the word may probably be a corruption of an Eastern name for the stone. The See also:colour of amethyst is usually attributed to the presence of See also:manganese, but as it is capable of being much altered and even discharged by See also:heat it has been referred by some authorities to an organic source. Ferric thiocyanate has been suggested, and See also:sulphur is said to have been detected in the See also:mineral. On exposure to heat, amethyst generally becomes yellow, and much of the See also:cairngorm or yellow quartz of jewellery is said to be merely " burnt amethyst." See also:Veins of amethystine quartz are See also:apt to lose their colour on the exposed outcrop. Amethyst is composed of an irregular superposition of alternate lamellae of right-handed and See also:left-handed quartz. (See QUARTZ.) It has been shown by Prof.

J. W. See also:

Judd that this structure may be due to See also:mechanical stresses. In consequence of this composite formation, amethyst is apt to break with a rippled fracture, or to show " thumb markings," and the intersection of two sets of curved ripples may produce on the fractured See also:surface a See also:pattern something like that of " See also:engine turning." Some mineralogists, following See also:Sir D. See also:Brewster, apply the name of amethyst to all quartz which exhibits this structure, regardless of its colour. The amethyst was used as a See also:gem-stone by the See also:ancient Egyptians, and was largely employed in antiquity for intaglios. Beads of amethyst are found in Anglo-Saxon See also:graves in See also:England. Amethyst is a very widely distributed mineral, but See also:fine clear specimens See also:fit for cutting as ornamental stones are confined to comparatively few localities. Such crystals occur either in cavities in mineral-veins and in granitic rocks, or as a lining in See also:agate geodes. A huge geode, or " amethyst-grotto," from near See also:Santa Cruz in See also:southern See also:Brazil, was exhibited at the See also:Dusseldorf See also:Exhibition of 1902. Many of the hollow agates of Brazil and See also:Uruguay contain a See also:crop of amethyst-crystals in the interior. Much fine amethyst comes from See also:Russia, especially from neat Mursinka in the See also:Ekaterinburg See also:district, where it occurs in drusy cavities in granitic rocks.

Many localities in See also:

India yield amethyst; and it is found also in See also:Ceylon, chiefly as pebbles. Purple See also:corundum, or See also:sapphire of amethystine tint, is called See also:Oriental amethyst, but this expression is often applied by jewellers to fine examples of the See also:ordinary amethystine quartz, even when not derived from Eastern See also:sources. Amethyst occurs at many localities in the See also:United States, but rarely fine enough for use in jewellery. Among these may be mentioned Amethyst See also:Mountain, See also:Texas; Yellowstone See also:National See also:Park; See also:Delaware Co., See also:Pennsylvania; See also:Haywood Co., See also:North Carolina; See also:Deer See also:Hill, and See also:Stow, See also:Maine. It is found also in the See also:Lake See also:Superior district. See G. F. Kunz, Gems b'c. of North See also:America (r89o),and See also:Report forr2th See also:Census (vol. "Mines and Quarries").

End of Article: AMETHYST

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