Process for producing amethyst crystal

Details Process for producing amethyst crystal Process for producing amethyst crystal

1973-12-06

1976-02-03

Yudkoff, Norman

Chemistry: physical processes

Physical processes

Crystallization

23300, 423335, 423339, 106 42, 252 629, B01j 1704, C01b 3312, B01j 1736

Patent

active

039362760

ABSTRACT:
A process for producing amethyst crystals which involves growing colourless quartz crystals by a hydrothermal method of a temperature drop in a high-pressure autoclave on crystalline quartz seed plates oriented parallel to pinacoid crystallographic planes {0001} or to planes inclined to said pinacoid planes at an angle of up to 15.degree. with the use of silica as a charge, said growing being effected from aqueous solutions of ammonium fluoride with a concentration of from 5 to 30% by weight and containing iron introduced into the autoclave in the form of its oxydic or hydroxydic compounds in an amount ranging from 5 to 30 g/l of the solution. Said growing of colourless quartz crystals is effected at a crystallization temperature within the range of from 150.degree. to 500.degree.C under a pressure of from 10 to 1,200 kg/cm.sup.2 and at a crystal growth rate of from 0.05 to 1.5 mm/day. It is preferable to introduce inorganic compounds of lithium or sodium into the autoclave, prior to the crystal growing, in an amount ranging from 0.5 to 2.0 g/l of the solution. The resulting grown colourless quartz crystals are exposed to an ionizing radiation. In the process of the present invention the crystal growing is effected under specified physico-chemical process parameters enabling a good reproducibility of said process. Crystal growth rates are high enough and the process according to the present invention makes it possible to produce amethyst crystals with a high colour purity (without any smoky tint) and with no cracks whatsoever.

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Brown et al., Nature, Jan. 5, 1952, Vol. 169, pp. 35-36.
White, Endeavorer, Apr. 1962, The Synthesis and Uses of Artificial Gemstones, pp. 73-84.
U.S. Patent 2,484,829, 10/49, Holden.
Tzinober et al., "Kristallographizer," Journal, 4, 633, 1959.

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