江苏某含铬镁铝榴石的宝石矿物学研究

Study on Gemological Mineralogy of Chromium-Containing Pyropes of Jiangsu Province

镁铝榴石,英文名称Pyrope来自希腊语,寓意矿物呈火焰般鲜红色。自古以来,镁铝榴石宝石颇为人民所赏识和珍藏。在宝石学上,镁铝榴石宝石归属主要宝石(Majorgem)类,并在世界宝石市场上一直是畅销的中档宝石品种。 江苏含铬镁铝榴石宝石最早为江苏第六地质队发现,已进行很多工作。作者在此基础上,拟对其宝石矿物学特征作一报导。

The samples studied are collected from the Quarternary residual drift bed. The chromian pyrope has been supposed to be derived mainly from the nearby porphyritic chromian pyrope-chrome diopside-enstatite-peridotite. The present stone has been well known on its bright red color, purity and transparency. The faceted gem reveals its excellent quality which may be comparable with the best known"Bohemian Ruby". The present pyrope is rather peculiar in color. When the quality of illumination is altered, the color of the mineral changes to such an extent that an alexandrite-like effect is seen. In transmitted daylight the pyrope appears reddish violet, in lamplight it is ruby-like red. The wave length of optical absorption spectra of Cr ions for the present pyrope is 5500-5600A, 4000-4100A. With its absorption spectra of Cr ions less than the critical value of 5800A and 4150A, the present pyrope appears red in color. The color indices of the transmition color of chromium-containing pyrope are Tvis 25.36 x 0.3649 y 0.3252 d-495nm Pc0.09.