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我国中、新生代碎屑岩系中的盐类矿床分布广泛,在这些矿床中几乎都有钙芒硝的沉积。过去一直把光轴角小（近于一轴晶）作为钙芒硝的重要鉴定特征之一,并以此特征在显微镜下区分钙芒硝和钾石膏（光轴角（2v）=28°18＇）。去年7月在鉴定云南某地的钙芒硝岩时,我们发现一颗光轴角大于20°的颗粒,当时怀疑它是否是钾石膏?出于找寻钾矿物的目的,我们在云南第一地质大队钾盐分队的大力支持和帮助下,开展了一系列的工作,初步结果证明:光轴角大于10°以上的颗粒是钙芒硝自身的光轴角变化,而不是其它矿物。
Salt deposits in the Mesozoic and Cenozoic clastic rocks are widely distributed in China. Almost all of these deposits contain glauberite deposits. In the past, the small optical axis (near-axis crystallinity) has been used as one of the important identification features of glauberite, and the characteristics of glauberite and potash gypsum were differentiated under the microscope (optical axis angle (2v) = 28 ° 18 ’) . Last July in the identification of glauconite in a certain place in Yunnan, we found a particle with an optical axis angle greater than 20 °, when it was suspected that it was a potash gypsum. For the purpose of looking for potash minerals, we found that in the Yunnan First Geological Brigade A series of work has been carried out under the strong support and assistance of the potassium salt unit. The preliminary results show that the particles with the optical axis angle larger than 10 ° are the changes of the optical axis angle of glauber’s salt rather than other minerals.