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巴西西阿拉 Tau祖母绿产于黑云母片岩和含有金云母及绿泥石的透闪石片岩内。其形成与侵入到该岩系中的深熔伟晶岩密切相关。祖母绿与大磷灰石晶体相伴出现,局部含刚玉。化学分析表明 Cr_2O_3及 V_2O_3(<0.25%,wt)的含量低,而 FeO(0.91～1.17%,wt)、MgO(2.42～2.69%,wt)及 Na_2O(1.69～1.96%,wt)含量较高.下列关系式表明了低 Al 含量:Al~(3+,VI)=(Mg,Fe)~(2+)+Na~+Al~(3+,VI)=(FeCr,V)~(3+,VI)Tau(?)祖母绿含大量的矿物包襄体,迄今,已鉴定有金云母,透闪石、辉钼矿、褐帘石和磷灰石。另外,有很小的液滴聚集或出现矿物尘埃及平面空穴。主要呈单相充填。这些包裹体的集中,降低了祖母绿的宝石品级。
Tau emerald in Western Alla is produced in biotite schist and tremolite schist containing phlogopite and chlorite. Its formation is closely related to the deep-melting pegmatite intruded into the rock system. Emerald and apatite crystals accompanied by the emergence of local corundum. The chemical analysis showed that the contents of Cr 2 O 3 and V 2 O 3 (<0.25%, wt) were low, while the contents of FeO (0.91-1.17%, wt), MgO (2.42-2.69%, wt) and Na 2 O (1.69-1.96% . The following relationship shows the low Al content: Al ~ (3 +, VI) = (Mg, Fe) ~ (2 +) + Na ~ + Al ~ (3 +, VI) = (FeCr, V) +, VI) Tau (?) Emerald contains a large number of mineral inclusions. To date, phlogopite, tremolite, molybdenite, polydatin and apatite have been identified. In addition, there is very little droplet aggregation or mineral dust and planar holes. Mainly single-phase filling. The concentration of these inclusions has reduced the emerald gem grade.