一种新型南非紫色玉石的矿物学特征研究  

Mineralogical Characteristics of A New Purple Jade from South Africa

作　　者：杜杉杉[1] 杨明星[1] 刘虹靓[1] 王含予 

机构地区：[1]中国地质大学珠宝学院,湖北武汉430074

出　　处：《宝石和宝石学杂志》2014年第1期19-25,共7页Journal of Gems & Gemmology

摘　　要：为探究南非最近产出的一种新型紫色玉石的矿物学特征及颜色成因,对其进行了常规宝石学特征测试,并采用X射线粉末衍射仪(XRD)、扫描电子显微镜(SEM)及紫外-可见分光光度计(UV-Vis)等仪器对其矿物组成、结构特征、化学成分和致色元素进行了研究。常规宝石学测试结果表明,该玉石折射率为1.54(点测),相对密度为2.1~2.2,摩氏硬度为1~2。XRD分析结果表明样品主要矿物组成为鳞镁铁矿,呈紫色,次要矿物成分为利蛇纹石,呈褐绿色;SEM分析结果显示鳞镁铁矿大多为集合体,主要以鳞片状和纤维状两种集合体形式存在,能谱分析(EDS)结果显示紫色部分主要化学成分为Mg,O,C,Fe,Cr等,佐证了紫色部分为鳞镁铁矿;UV-Vis结合EDS分析结果显示,鳞镁铁矿的紫色可能由Cr致色引起。A new purple jade has been found in South Africa recently. In the article, mineral assemblages, structural characteristics, chemical components and the main colour causing el- ements were investigated by means of X-ray diffraction （XRD）, scanning electron microscope （SEM）, and ultraviolet-visible spectrophotometer （UV-Vis） . The testing results show that the refractive index of the jade is 1.54 （point measure- ment） and the specific gravity is 2. 13-2. 14. The special gravity increases slightly along with the content increase of brownish green mineral. When nails swipe the surface of sam- ples, power easily fall off, which indicates its Moh＇s hardness is 1 to 2. The colour of the jade differs slightly from dark purple to light purple and the opaque jade has a rare silk luster. Mineral component was investigated by X-ray diffraction produced by the German Bruk- er, AXS DS-FOCUS models. Owning to the fact that the separation of the purple minerals and brownish green mineral was quite difficult, the two testing parts of the samples were visually relatively pure purple mineral and mixture of purple mineral and brownish green mineral. The samples were grided into powder of 200# screening and dried. Retrieving the X-ray diffraction pattern of the sample with the software of JADE, the authors found that dvalues at strong peaks equaled to 7. 842 5 A（003）, 3. 925 7 A（006）, 2. 618 9 A（012） and d values at some weak peaks equaled to 2. 332 6 ,A（015） ,1. 985 3 A（018）, 1. 521 5 A（113）. The characteristic peaks and intensities were corresponding with those of pyroaurite. The re- suits also showed the mineral component of the brownish green part is lizardite. Chemical composition and structural characteristics of samples were studied by scanning electron microscope（SEM） and its attached energy dispersive（EDS）. The results showed from three main aspects. Firstly, pyroaurite from the samples mainly occurs as mineral ag- gregates. Most are flaky texture, with only some fibrous t

关 键 词：紫色玉石 鳞镁铁矿 矿物学特征 致色 

分 类 号：TS93[轻工技术与工程]