TRAVELS IN BRAZIL. 173 



and forms veins several feet tliick. Emeralds are seldom 

 found in gneiss, but always in mica : when this latter is 

 soft, and almost unctuous to the touch, the emeralds con- 

 tained in it are larger, of a more beautiful green, per- 

 fectly formed, and the lateral planes clear of the matrix. 

 They are never found massive, but the crystals dissemin- 

 ated, and confusedly aggregated in the mica, very rarely 

 embedded in quartz ; in the latter case they are greenish 

 white, or even white, as the quartz itself." 



These emerald crystals too are full of impressions of the 

 surrounding mica, like the topaz and the euklase ; so that 

 the original repository of the latter appears to be the 

 less liable to any farther doubt. 



If, in addition to this origin of the emerald, we farther 

 consider that the pycnite, which is the nearest allied to the 

 topaz in its component parts, likewise occurs in mica ; if we 

 attend to the occurrence of the topazes in the topaz rock and 

 lithomarge at Auerbach, in Saxony, we shall find their 

 repository and that of the euklase in Brazil, which is akin 

 to the emerald, little or not at all varying from that known 

 in Germany, and thus have another proof that in this re- 

 spect also the inorganic new world is conformable to the old. 

 Even the modified mica, the scaly lithomarge, or Mr. Mawe's 

 earthy talc, is met with in Bavaria, namely, in the country 

 from WaltershofF to PuUenreuth, for an extent of two 

 leagues, so nearly resembling that from the district of 

 Capao, that it is often very difficult to distinguish them. 

 Only the mode of occun-ing is different ; while, if the latter 

 is to be regarded as a considerable bed, the former, accord- 

 ing to Mr. Von Flurl's Description of Mountains, p. 424. 

 sometimes forms a flcJtz stratum of great extent, and three 

 fathoms thick, in which lies a compact and fibrous brown 

 iron-stone, and in conjunction with this even a kind of 

 talc-Uke, or micaceous iron-stone, which is rather allied to 

 mica. Several flotz deposits of this modified mica, or earthy 

 talc, are described by Dr. Reuss, in his Orographie des 



