Nephrite Jade from Guangxi Province, China
2014; Gemological Institute of America; Volume: 50; Issue: 3 Linguagem: Inglês
10.5741/gems.50.3.228
ISSN2376-4473
AutoresZuowei Yin, Cui Jiang, M. Santosh, Yiming Chen, Yifang Bao, Quanli Chen,
Tópico(s)Cultural Heritage Materials Analysis
ResumoNephrite jade with high market value and production potential from the Chinese city of Hechi, in Guangxi Province, was tested by standard gemological methods, polarizing microscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, and energy-dispersive spectrometry (EDS).The three samples were mainly white and gray-white (with areas of gray, gray-green, dark green, and black) and had a greasy to waxy luster.Within each of these color varieties, the samples exhibited either "band" or dendritic patterns.The band pattern, composed of tremolite, varied in shape and was either transparent or opaque.Its color, transparency, and distribution were different from the unpatterned areas.The dendritic patterns, which had a brownish yellow and dark brown to black color, were composed of chlorite that formed during metamorphism.N ephrite is favored by Chinese collectors for its color and luster, as well as its fine texture and outstanding toughness.Primary nephrite deposits are found in more than 20 countries, including China, Russia, Canada, Australia, New Zealand, and South Korea.Chinese deposits are mainly distributed in the areas of Xinjiang, Qinghai, Guizhou, and Liaoning (Liao et al., 2005;Zhang et al., 2011).Research shows that nephrite's excellent toughness is a product of its fine-grained interlocking structure (Bradt et al., 1973;Dorling and Zussman, 1985;Yang, 2011).Its green color is due mainly to the substitution of Cr 3+ and Fe 2+ for Mg 2+ (Flint, 1990).In principle, nephrite can form in two different ways.One is by contact metasomatism between intermediate-acidic intrusive
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