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Abstract:
Jadeite jade, also called Feicui in China, is the most popular jade variety and one of the best selling gems in China. Colour and transparency are the primary quality factors that determine the value of Feicui. Jadeite jade is a polycrystalline aggregate, primarily consisting of jadeite (NaAlSi2O6) and including accessory minerals such as omphacite, albite, amphibole, and chromite[1-2]. Gem-quality Feicui material is only found in a few countries, namely Myanmar, Guatemala, Russia, Kazakhstan, and Japan[3-5]. Myanmar is the traditional and most important producer of gem-quality jadeite jade, while Guatemala has become the second-largest producer[6]. "Ice jade" is a translucent variety of jadeite jade (also known as Feicui) that is generally of high value. Reportedly from the Morales mine in the Izabal Department of Guatemala, it has recently appeared in the Chinese jewelry market. In this study, the structural characteristics, mineral compositions, and colour genesis of Guatemalan "ice jade" were studied using UV-Vis-NIR and Raman spectroscopy, X-ray diffraction, electron probe microanalysis, scanning electron microscopy, and cathodoluminescence.
"Ice jade" from the Morales mine in Guatemala is composed of almost pure jadeite, containing very small amounts of accessory minerals, including omphacite and albite. The omphacite grains are often nearly colourless and not easily observed, while the albite grains cluster as white snowflake-like inclusions or dispersed as small specks. The "ice jade" exhibits a fine-grained structure, occasionally coexisting with a micro-granular structure. The relatively pure chemical compositions of sodium pyroxene accompany with a fine texture produced a transparent to semi-transparent and near-colourless appearance. A small amount of dispersed fine-grained omphacite is considered the cause of the pale green colour in "ice jade" from Guatemala. The Guatemalan origin can be determined from its characteristic appearance, microstructure, accessory minerals, and chemical compositions.
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Keywords:
- "ice jade" /
- jadeite /
- albite /
- translucent /
- Guatemala
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