“撒金花黑青玉”的宝石学特征与成因矿物学研究

Gemmological Characteristic and Genetic Mineralogy on Pyrite-Chlorite-Bearing Actinolite Jade

  • 摘要: “撒金花黑青玉”是市场中新出现的一种玉石,整体为墨绿色,表面可观察到明显的黄色金属矿物。采用偏光显微镜、X射线粉末衍射仪、扫描电子显微镜、电子探针等测试手段,对“撒金花黑青玉”的结构、矿物组成和成因进行了深入分析。测试结果显示:(1)“撒金花黑青玉”主要矿物成分为绿泥石(45%)、阳起石(45%)、黄铁矿(10%),其中绿泥石为三八面体结构;(2)阳起石呈纤维状变晶结构,绿泥石呈鳞片状变晶结构,黄铁矿呈浸染状分布于由绿泥石与阳起石组成的玉石内;(3)样品中阳起石主量元素组成在透闪石-阳起石-铁阳起石的Mg/(Mg+Fe2+)-Si分类图解中进行投点,落在阳起石范围内,与X射线粉末衍射结果一致。样品内绿泥石在Fe-Mg-(Al+□)分类图解中投点落在镁绿泥石与Ⅰ型三八面体绿泥石范围内;(4)阳起石中Mg/(Mg+Fe2+)值(=0.89)、绿泥石中Al/(Al+Mg+Fe)值(< 0.35)与绿泥石中较高的Mg/(Mg+ Fe)(=0.85)指示样品原岩为富镁超基性岩;(5)利用绿泥石化学成分标型对其形成环境进行估算,结果指示样品形成于相对还原的中低温环境且经历多期变质作用。鉴于“撒金花黑青玉”中含有较多的绿泥石组分以及形成环境与软玉具有较大的差异,依据现行国标,不建议将“撒金花黑青玉”定名为和田玉,建议定名为阳起石质玉(含绿泥石)。

     

    Abstract: Pyrite-chlorite-bearing actinolite jade, that has dark green colour with yellow minerals disseminated in it, is a new kind of jade appearing in the market. In order to deeply understand the structure, mineral components, and genetic information of the pyrite-chlorite-bearing actinolite jade, X-ray diffractometer, polarizing microscope, scanning electron microscope, electron probe micro-analyzer, and other test methods were employed. The results showed that: (1)The main mineral components of the pyrite-chlorite-bearing actinolite jade were trioctahedral chlorite (45%), actinolite(45%), and pyrite(10%); (2)The actinolite was fibrous crystalloblastic structure and the chlorite was of lepidoblastic texture, with pyrite embedded in the jade composed of chlorite and actinolite; (3)Plots of the major elemental components of actinolite in the Mg/(Mg+Fe2+)-Si of tremolite-actinolite-ferroactinolite classification diagram was within the range of actinolite.The sample chlorite in the Fe-Mg-(Al+□) classification diagram was plotted within the range of amesite and Type Ⅰ trioctahedral chlorite; (4)The values of the Mg/(Mg+Fe2+)≈0.89 of the actinolite and the Al/(Mg+Fe) < 0.35) and the Mg/(Mg + Fe) =0.85) of the chlorite indicate that the protolith of the sample is magnesium-rich ultrabasic rock; (5)By predicting the formation environment based on the typomorphic chemical composition of chlorite, the result showed that the sample was formed in a relatively reduced environment of medium and low temperature and should have undergone multistage metamorphisms during the formation process. Considering the pyrite-chlorite-bearing actinolite jade contains substantial content of chlorite, as well as the environment of formation which are different from nephrite, the pyrite-chlorite-bearing actinolite jade studied here was not recommended to name as Hetian Yu according to the current national standard.It is suggested that the sample may named as actinolite jade (containing chlorite).

     

/

返回文章
返回