【摘要】 石榴石发现于福建省的明溪宝石矿区。与其共生的有蓝宝石和锆石等。明溪的石榴石有两种类型。一种为紫红色 ,主波长为 585～ 588nm,饱和度为 0 .569～ 0 .62 9;另一种为褐红色 ,主波长为 60 0～ 595nm,饱和度为 0 .866～ 0 .939。前者的折射率为 1 .74 ,密度为 3.65～ 3.78g/cm3;后者的折射率为 1 .75～ 1 .76,密度大于 3.8g/cm3。在 Webster( 1 983)的 RI—D图上 ,前者属镁铝榴石。大多数褐红色的石榴石落在铁铝榴石 -镁铝榴石区域内。这一结论得到了电子探针和 X射线分析的支持。这些分析还表明 ,紫红色的石榴石中含有较高的 Cr,而褐红色的石榴石中则富含 Fe和 Ti。在明溪石榴石的吸收光谱中紫红色石榴石具有 4 1 0 nm和570 nm的吸收带 ,这是由于晶体中存在 Cr3+造成的 ;褐红色石榴石则出现一个 4 0 0～ 590 nm的吸收带更多还原

【Abstract】 Garnets have been found in Mingxi gemstone deposit, Fujian Province, associated with sapphires and zircons. There are two types of garnets. One is purplish red, with main wavelength of 585～588nm and saturation of 0.569～0.629 in their chromatic measurement; the other is brownish red, with main wavelength of 600～595nm and saturation of 0.866～0.939. The purplish red garnet has refractive index of 1.74, density of 3.65～3.78g/cm 3 and brownish red garnet, 1.75～1.76 and over 3.8g/cm 3 respectively. In the RI-D diagram of Webster(1983), the purplish red garnet belongs to the category of pyrope and most of brownish red garnets fall in the area of almandine pyrope. The conclusion is conformed to the microprobe analyses and X ray diffraction, which also show that the purplish red is high in Cr while the brownish red high in Fe and Ti. As for the optical absorption spectra of Mingxi garnets, the purplish red has absorption bands at 410 and 570 nm due to Cr 3+ in the crystals and the brownish red shows the broad absorption band from 590～400nm with the absorption peaks at 410nm and 510nm.更多还原