Mineralogy of Jadeite

• Main Author: 湯惠民
• Other Authors: 譚立平
• Format: Others
• Language: zh-TW
• Published: 1995
• Online Access: http://ndltd.ncl.edu.tw/handle/65362993412483629480

碩士 === 國立臺灣大學 === 地質學研究所 === 83 === 　　Jadeite is a vary valuable gemstone; however it occurs generally as an aggregate and never as a single crystal. Jadeitite, the rock composed mainly of jadeite, is a proper name for all the jadeite jade sold in the market. The major mineral of jadeitite is jadeite; however, jadeite generally contains diopside, acmite and kosmochlor molecules in solid solution. Jadeite often associates with minerals of the amphibole group such as tremolite, edenite and richterite. Chromite, grossularite, rutile and ilmenorutile are commonly associated with jadeite. 　　A total of 127 samples were studied. This research emphasizes physical properties (specific gravity "S. G.", hardness and refractive index "R.I.") of the jadeite. The specific gravity of jadeite is from 3.20 to 3.47, Mohs hardness from 6.2 to 6.8, and refractive index from 1.643 to 1.670. 　　The writer, based on this research, proposes that jadeitite is mainly a three-component solid solution of jadeite (including kosmochlor)-diopside-acmite. According to this type of classification, jadeitite can be separated into three groups: 1) pure jadeite (jadeite more than 80%, white part 93~98%), 2) diopside-jadeite type (jadeite 46~70%, diopside 7~45% and acmite 2-5%), and 3) acmite-jadeite type (jadeite 24~76%, acmite 19~43% and diopside 5~33%). The acmite-jadeite type is usually called "dark green jade". 　　The Cr2O3 content in green jadeite (from light-green, apple-green to dark green) ranges from 0.16 to 3.14%. The most favorable one is brilliant green, caused by the presence of kosmochlor which contains high Cr2O3. 　　Most peaks of natural jadeite under the Raman spectroscope are between 200 and 1100cm-1. The major absorption peaks include 214, 367, 690 and 1032cm-1. The bleached and polymer-impregnated jadeites of this study have peaks between 1100and 180cm-1, including 1105,1179, 1226, 1282, 1450, 1601 and 1700 cm-1 etc.. Due to different compositions of the polymers, the number and site of peaks vary.