Mineralogical, chemical, and spectroscopic properties of chrysoberyl crystals recovered from sapphire placer deposits, related to Tertiary volcanic rocks, in the New England gem fields in New South Wales (NSW), Australia, are presented. The samples appeared yellow, yellowish brown, or brown in transmitted light, and some crystals revealed a distinct sectorial zoning between brown i (011) and yellow o (111) growth areas. In reflected light, the i sectors showed a whitish appearance, and cabochon-cut samples with larger whitish i sectors displayed chatoyancy. On the basis of morphological properties, trace-element contents, and absorption spectra, the chrysoberyl samples were subdivided into four different groups, possibly originating from different host rocks. The largest such group, comprised of samples with distinct sectorial color zoning, also revealed a pronounced variation in trace-element levels of titanium, niobium, and tantalum between the different growth sectors. Smaller variations were found for boron, magnesium, and iron, and almost no variation was observed for gallium.
Chrysoberyl recovered with Sapphires in the New England placer deposits, New Southwales, Australia
CAUCIA, FRANCA PIERA;
2016-01-01
Abstract
Mineralogical, chemical, and spectroscopic properties of chrysoberyl crystals recovered from sapphire placer deposits, related to Tertiary volcanic rocks, in the New England gem fields in New South Wales (NSW), Australia, are presented. The samples appeared yellow, yellowish brown, or brown in transmitted light, and some crystals revealed a distinct sectorial zoning between brown i (011) and yellow o (111) growth areas. In reflected light, the i sectors showed a whitish appearance, and cabochon-cut samples with larger whitish i sectors displayed chatoyancy. On the basis of morphological properties, trace-element contents, and absorption spectra, the chrysoberyl samples were subdivided into four different groups, possibly originating from different host rocks. The largest such group, comprised of samples with distinct sectorial color zoning, also revealed a pronounced variation in trace-element levels of titanium, niobium, and tantalum between the different growth sectors. Smaller variations were found for boron, magnesium, and iron, and almost no variation was observed for gallium.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
