Taijin Lu

Industrial growth, morphology and some properties of Bi-colored amethyst–citrine quartz (ametrine)

In the middle of the 1990s the first industrial technology for producing synthetic bi-colored amethyst–citrine quartz (ametrine) was created. The technology is based on results of studies of the effect of different physical–chemical and growth factors on the formation, stability and the character of the distribution in crystals of amethyst and citrine color centers.

Hydrothermal Synthetic Red Beryl from the Institute of Crystallography, Moscow

42 SYNTHETIC RED BERYL GEMS & GEMOLOGY SPRING 2001 both natural and synthetic, plus Ti, Co, and Ni in synthetic beryls; Sinkankas, 1981; Fritsch and Rossman, 1987). These elements substitute for Al. Alkali elements (Li, Na, K, Rb, Cs) can also occur in minor amounts by substituting for Be and Al (Sinkankas, 1981; Aurisicchio et al., 1988; Deer et al., 1997, pp. 378–386); however, these elements do not affect beryl coloration. The beryl crystal structure contains two different sites along “open” channels that can incorporate water molecules (Schaller et al., 1962; Wood and Nassau, 1968; Schmetzer, 1989; Deer et al., 1997). These variations in transition metal, alkali element, and water contents in beryls cause differences in physical properties (such as refractive index, specific gravity, and color), as well as in visible and infrared absorption spectra.

Observation of etch channels in several natural diamonds

Abstract We report the characteristics of dissolution etch channels (open tubes), with various forms ranging from parallel lines to irregular ribbon or worm-like shapes, in seven natural gem-quality diamonds. These channels have openings at the surface with rhombic or modified rhombic shapes, and internally, they often terminate at solid inclusions. They appear to originate either from the outcrop of a bundle of dislocations, or along dislocation dipoles elongated along the 〈110〉 direction. As the dissolution process proceeds, the penetration direction of an etch channel may change as a result of the interaction with other growth defects. Many of the etch channels we observed exhibit highly irregular forms. Possible relationships between the etch channels and lattice defects are discussed.

Russian Synthetic Ametrine

Gem-quality synthetic ametrine has been produced commercially in Russia since 1994, by hydrothermal growth from alkaline solutions. Faceted synthetic ametrine has many similarities to its natural counterpart from Bolivia. For the most part, however, the synthetic ametrine obtained for this study could be identified by a combination of characteristics, including growth features such as twinning and color zoning. EDXRF chemical analyses revealed higher concentrations of K, Mn, Fe, and Zn than in natural ametrine. IR spectra of the synthetic citrine portions showed more intense absorption in the 3700-2500 cm^(-1) range compared to natural ametrine; the synthetic amethyst zones showed a weak diagnostic peak at 3543 cm^(-1).

Channel structures observed in natural diamonds, synthetic moissanite, and synthetic quartz

Internal growth and dissolution features are visual characteristics of some natural, synthetic, and treated gem materials. Open channels or need-like structures are occasionally observed in natural diamond, synthetic moissanite (SiC-6H), and chemically-etched synthetic colorless quartz. The distinguishing features among the channel structures in these materials are compared, and possible formation mechanisms of the channels associated with dislocations or dislocation bundles are discussed.

Growth and characteristics of some new varieties of coloured quartz single crystals

Abstract Methods for the hydrothermal synthesis of four new coloured varieties of quartz have been developed. Two of these varieties are very rare in nature. They are a bi-coloured amethyst-citrine quartz (ametrine) and a phosphorous-bearing low-temperature pink quartz. The other two varieties have no natural counterparts. They are a pink-violet Ni-bearing quartz, and a Cu-bearing quartz which resembles aventurine. The principal conditions for producing these varieties of quartz single crystals are described.