【摘要】 翠榴石（Demantoid）是一种稀少的贵重宝石矿物。本文的新疆含铬翠榴石在我国属首次发现。通过化学成分、X射线粉晶衍射、穆斯堡尔谱、红外及可见吸收光谱等测定确认,新疆翠榴石所含钙铁榴石端员分子均在90%以上,接近于纯端员组成,Fe²⁺含量低于穆斯堡尔谱最低检出界限。在这里,绿色与占据八面体位置的Fe³⁺直接相关,而微量Cr³⁺的存在则使其翠绿色色调大大加强。结合翠榴石产出地质条件及矿物共生组合分析可以认为,在超镁铁质岩体中残存的挥发分作用下出现了橄榄石、辉石被蛇纹石交代的现象,形成贫铝富铁的结晶环境。后期侵入的岩浆热液沿蛇纹岩裂隙交代促使石棉脉中翠榴石的结晶沉淀,而局部范围内的挤压错动则造成了由蛇纹石石棉“胶结”的翠榴石“团块”,翠榴石中含的微量铬来源于超镁铁质岩中的铬铁矿和铬尖晶石。更多还原

【Abstract】 Demantoid is a rare precious gen mineral.The mineral-Cr-demantoidreported in this paper has been discovered for the first time in China.Chemicalanalysis,X-ray powder diffraction,M（o|¨）ossbauer spectroscopy,IR and visibleabsorption spectrometry have revealed that the end-member molecules of andra-dite contained in Xinjiang demantoid are more than 90%,close to the pure end-me（?）ber compositon.The content of Fe²⁺ is beyond the detection limit of M（o|¨）-ssbauer spectroscopy.The green colour is related to Fe³⁺ in the octahedral site,while the presence of trace Cr³⁺makes the mineral more jade green.It is con-sidered from the geological occurrence and mineral association of demantoidthat under the action of residual volatiles in ultramafic rock bodies olivine andpyroxene would be replaced by serpentine,creating a crystallization environmentcharacterized by A1/Fe enrichment.Metasomatism by magmatic hydrothermalsolutions through the fissure of serpentinite in the later stages promoted thecrystallization and precipitation of demantoid in asbestos veins.Local compression and dislocation gave rise to"massive"demantoid cemented by serpentineasbestos.Evidence shows that the trace Cr in demantoid was derived from chro-mite and Cr-spinel in the ultramafic rock bodies.更多还原