“樱花玛瑙”的宝石矿物学特征

Mineralogical and Gemmological Characteristics of“Sakura Agate”

“樱花玛瑙”是目前中国珠宝市场上较新的玛瑙品种,拥有特征的“樱花状”包裹体,常见颜色为无色-粉色。通过手标本观察、偏光显微镜观察、常规宝石学测试、红外光谱、显微拉曼光谱、电子探针、微区X射线荧光分析和EDS能谱仪等测试方法分析“樱花玛瑙”样品的宝石学特征、矿物组成、结构和不同颜色的形成原因。结果显示,“樱花玛瑙”样品中基质和包裹体的主要矿物组成均为α-石英,且基质中还含有少量的斜硅石;基质为隐晶质石英,包裹体为显晶质石英。“樱花玛瑙”样品的颜色差异源于其所含微量元素的种类和质量分数,粉橘色基质主要是由Mn和Fe元素致色,少部分“樱花玛瑙”中还含有绿色包裹体,其主要是由Fe元素致色。“樱花状”包裹体存在石膏和重晶石颗粒,表明在包裹体形成时,含矿流体富钡(生物钡)和钙,同时可能有含硫酸盐的孔隙水混入,成矿条件不稳定。

“Sakura agate”is a relatively new kind of agate in the domestic market.It has the characteristic“sakura-shape”inclusions and its common colour is colourless-pink series.The gemmological characteristics,mineral components,structure and the formation of different colours of“Sakura agate”were studied by hand specimens observation,polarizing microscoic observation,conventional gemmological tests,infrared spectrometer,micro-Raman spectrometer,electron probe,micro-area X-ray fluorescence analysis and EDS.The results showed that the main mineral components of the substrate and inclusions of“Sakura agate”areα-quartz while a small amount of moganite can be found in substrate.The substrate is cryptocrystalline quartz,while the inclusion is consist of crystalline quartz.The colour difference of“Sakura agate”is due to the different types and contents of trace elements.The pink-orange substrate is mainly caused by Mn and Fe elements,while the rare green inclusions are mainly caused by Fe elements.There are some gypsum and barite grains in inclusions,indicating that when the inclusions are formed,the ore-forming fluid is rich in barium(biological barium)and calcium,and there might be sulfate-containing pore water mixed in,resulting in the unstable mineralization conditions.