白岗石是花岗石的一种特殊类型,20多年前国外已有报道。在我国,除北京西山外,贵州省的梵净山也有发现。梵净山白岗石为白色和灰白色,一般为块状构造,坚硬,几乎无风化表层,在偏光显微镜下,呈清楚的花岗结构。其矿物颗粒大小在0.3～2毫米之间。梵净山白岗石的组成矿物有以下特点:①石英含量高达40%,而普通花岗石的石英含量<30%。⑧钾长石和斜长石全为白色或灰自色,而普通花岗石中的钾长石为肉红色,斜长石为灰色或浅灰色。⑧基本上无暗色矿物,白云母含量较多,约占12%,这也是 Baigang Stone is a special type of granite, which has been reported abroad more than 20 years ago. In China, besides Beijing Xishan, Fanjing Mountain in Guizhou Province has also been discovered. The white sandstone of Fanjingshan Bailang is white and off-white, generally a massive structure, hard, with almost no weathered surface, under a polarized microscope, a clear granite structure. Its mineral particle size is between 0.3 and 2 mm. The compositional minerals of the Baijingshi of Fanjingshan have the following characteristics: 1 The quartz content is as high as 40%, while the ordinary granite has a quartz content of less than 30%. 8 Potassic feldspar and plagioclase are all white or ash self-colored, while ordinary feldspars are red in meat, and plagioclase is gray or light gray. 8 There are basically no dark-colored minerals, and the muscovite content is relatively high, accounting for about 12%.