V. S. Balitsky

Growth of germanium dioxide single crystals with α-quartz structure and investigation of their crystal structure, optical, elastic, piezoelectric, dielectric and mechanical properties

The optimal growing conditions for α-GeO2 single crystals and Si-substituted α-GeO2 crystals have been found. The quality and sizes of the grown crystals of α-GeO2 have allowed studying their morphology, internal constitution and measuring their piezoelectric, dielectric, elastic and other physical properties.

Growth and characterization of GeO2 single crystals with the quartz structure

A new method for growth of the α-GeO2 single crystals from recycled hydrothermal solutions is described. The most important feature of the method is connected with existence and relatively high solubility of metastable quartz-like α-GeO2 in the aqueous solutions at the temperatures lower than 180–200°C, where the tetragonal (rutile-like) phase is thermodynamically stable. The heated aqueous solution is recycled according to the scheme: liquid → vapor → liquid. The partial evaporation of the solvent → vapor condensation → saturation of α-GeO2 in condensate → condensate flow down to the initial solution → crystallization of α-GeO2 on the quartz seeds are considered as the main successive stages of the process. Crystals of α-GeO2 with mass 300 g were obtained in a closed cylindrical steel vessel with the capacity of 2000 cm3. The maximal crystal growth velocity (up to 0.5 mm/day) was fixed in the [0 0 0 1] direction and the following relationship between the velocities of crystal growth to different directions was found to be: V[0 0 0 1] > V[1 1 2 1] > V[1 1 2 0] > V[1 1 2 0] ∼ V[1, 1 2 1] > V[0 1 1 1] ∼ V[1 0 1 1] > V[1 0 1 0]. Crystals of Si-substituted α-GeO2 with SiO2 content up to 7.5 wt% were also obtained. They can be characterized by a decrease in lattice parameters and by the higher temperature GeO2 phase transition from the quartz structure to the rutile structure. The morphology and some physical properties of the crystals were determined.

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.

Experimental Study of the Interaction of Mineral-Forming Hydrothermal Solutions with Oil and Their Joint Migration

Interaction between oil and hydrothermal solutions of different compositions was experimentally studied in a wide range of temperature (260–490°C) and pressures (8–150 MPa). This study was based on a new technique involving simultaneous occurrence of water-hydrocarbon interaction and growth of quartz, calcite, and fluorite crystals with fluid inclusions from the same solution. Fluid inclusions were studied to characterize the behavior of oil and aqueous solutions at elevated and high temperatures and pressures. It was shown that, owing to interaction with hydrothermal solutions, oil is intensely removed from the source rock and accumulated in the frontal part of hydrothermal convective flow. During this process, the oil is partially transformed into hydrocarbons, light oil, semiliquid and solid bitumens. At temperatures of 300–350°C and pressures of 50–100 MPa, oil and its fractionation products migrate in hydrothermal solution mainly in a drop-liquid state. At higher temperatures (360–395°C), when the oil/water ratio in the initial mixture is no higher than 1/70–1/35, liquid and gaseous hydrocarbons are completely dissolved in hydrothermal solutions forming a complex homogenous water-hydrocarbon fluid. The fluid can exist and migrate in this state, but it becomes heterogeneous with decreasing P-T parameters. Under favourable structural and lithological conditions, this can lead to the formation of displaced oil-and-gas deposits, with oil enriched in light components. The experiments unambiguously confirmed the concept that bitumen inclusions in minerals can serve as indicators of hydrocarbon migration paths in the Earth’s crust.

Russian Synthetic Pink Quartz

Transparent crystals of facet-grade synthetic pink quartz, produced by hydrothermal growth from a fluoride solution and subsequent treatment, have been commercially available since 1994. The characteristic properties that distinguish this material from its natural counterpart are a tabular crystal morphology with two large, well-developed basal faces; color bands parallel to the basal faces and the seed plate; two-phase inclusions adjacent and perpendicular to the seed plate; and an intense broad band around 3420 cm-1 in the infrared spectrum. Color stability and cause of color in synthetic pink quartz are briefly discussed.

Generation of Brazil and Dauphiné twins in synthetic amethysts

The generation of both Brazil and Dauphiné twins is triggered by strain fields associated with the fluctuation of growth parameters when solid inclusions of goethite (?) are precipitated on to a growth surface. Brazil twins are generated either directly from solid inclusions of smaller size or dislocations originating therefrom, whereas Dauphiné twins are generated only directly from solid inclusions of larger size. Precipitation of polymerized embryonic particles of SiO2 on the surface of solid inclusions is considered to be responsible for the generation of Brazil twins, whereas for Dauphiné twins it is necessary that embryonic particles precipitated in twin orientation on the surface of solid inclusions grow beyond a critical size.

The 3543 cm -1 Infrared Absorption Band in Natural and Synthetic Amethyst and Its Value In Identification

tionship between conditions of formation and the absorption spectra of natural and synthetic amethyst in the 3800–3000 cm-1 region to determine whether infrared spectroscopy can be used to identify synthetic origin (see Balitsky et al., 2003, 2004). Previously it was shown that both natural amethyst and synthetic amethyst grown in alkaline solutions share similar spectral features in this region (Balakirev et al., 1979; Zecchini, 1979; Balitsky, 1980; Lind and Schmetzer, 1980; Zecchini and Smaali, 1999). Two absorption bands are almost always present in both types—an intense feature at 3585 cm-1 and a relatively weak one at 3612 cm-1— due to the presence of OHdefects in the quartz structure (Rossman, 1988). Also characteristic is a broad band with a maximum near 3400 cm-1, which often overlaps the absorption bands mentioned above, that is related to the presence of The proper use and limitations of IR spectroscopy for identifying natural versus synthetic amethyst of various types have been investigated, focusing on the region 3800–3000 cm-1. The presence of absorption bands at approximately 3680, 3664, and 3630 cm-1 unambiguously proves artificial origin, but only for samples grown in near-neutral NH4F solutions. Conversely, there are no unambiguous diagnostic features in the IR spectra of the more commercially significant synthetic amethyst grown in alkaline K2CO3 solutions. Nevertheless, previous investigators have found potential diagnostic value in absorption bands at approximately 3595 and 3543 cm-1. Although the 3595 cm-1 band is not found in the spectra of synthetic amethyst, it also is frequently absent from those of natural amethyst. The 3543 cm-1 band is found in the vast majority of synthetic amethysts grown in alkaline solutions, but this band also is sometimes present in natural amethyst—so it provides only tentative evidence of synthetic origin. Moreover, the 3543 cm-1 band is absent from some varieties of synthetic amethyst. The unambiguous identification of natural versus synthetic amethyst therefore must be based on a combined examination of the IR spectra, internal growth structures (including twinning), and inclusions.

Brazil twinning in natural and synthetic amethyst crystals

Abstract The structures of Brazil twin boundaries, the micro-textures due to Brazil twinning, and the sites and the conditions for the generation of Brazil twins have been investigated on natural amethyst crystals with and without Brewster fringes, synthetic amethyst crystals hydrothermally grown under various conditions, and natural milky quartz crystals of epithermal origin. Their generation is triggered by the precipitation of solid inclusions on the growing smooth surfaces due to a perturbation of growth parameters. Brewster fringes appear through a process of incorporation of a large number of Brazil twin lamellae, whereas fibrous or other micro-textures appear when there is no such process. The former is assumed to have been formed under more stable conditions than the latter.

Kinetics of dissolution and state of silica in hydrothermal solutions of Na2CO3 and NaOH, and accelerated method for the quartz crystal characterization against growth rate

Abstract Kinetics of dissolution of quartz, its solubility and a heavy phase formation in Na2CO3 and NaOH solution under temperature 100°C, 200°C and 320°C and filling of autoclaves at 76% and 79% were studied. The etching surface of quartz bars after the runs is characterized. For the evaluation of entrapped solid inclusions and water-bearing nonstructural contaminations against the growth rate of quartz crystals, the accelerated method was developed.

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).