Synthetic alexandrites grown by the HOC method in Russia: internal features related to the growth technique and colorimetric investigation

Abstract

The estimated densities of the H 2 S phase (0.58 to 0.77g/cm 3) in isolated and fracture-bound multiphase inclusions in tanzanite have been used to model equilibrate and the contents will be lost through leakage and/or decrepitation. The internal pressures beyond which 'typical' microscopic inclusions in zoisite will leak (P d) but for larger inclusions (>100 μm) this value will be much lower. Thermophysical 10 μm) inclusions in zoisite would not survive the heating process to temperatures but the largest (c. 100 μm) will decrepitate or leak at even lower temperatures. Alignment of planar groupings of re-equilibrated inclusions will produce zones of investigation (Taylor et al., 2013) that microscopic H 2 S inclusions (c. 20 to 100 μm) not been heat treated.

Vanadium- and Chromium-Bearing Pink Pyrope Garnet: Characterization and Quantitative Colorimetric Analysis

“…The Usambara effect and color change are two manifestations of the phenomenon of having two distinct transmission windows in the visible spectrum. This study quantitatively described the interplay between color change and the Usambara effect (Schmetzer et al, 2013).…”

“…Liu et al (1999b) suggested that this tourmaline should only be considered a color-change stone within a certain range of path lengths. Schmetzer et al (2013) studied a synthetic alexandrite crystal and analyzed the relationship between the "alexandrite effect" and the Usambara effect in this pleochroic mineral with varying thickness. To shed more light on this phenomenon, we have carried out a detailed quantitative study of the influence of path length on color difference and hue angle difference under both lighting conditions for three different garnets.…”

Usambara effect in tourmaline: optical spectroscopy and colourimetric studies

“…1). Note that the Usambara effect was recently also established on Tanzanian gem-quality chromium-and vanadium-bearing garnets of spessartine-pyrope composition (Krzemnicki, 2014) and in some types of synthetic alexandrite (Schmetzer et al, 2013).…”