TRAVELS IN BRAZIL. 169 



pieces ; soiling ; adhering but little to the tongue ; not re- 

 markably heavy, but almost light. This scaly lithomarge, 

 which, on account of its very greasy feel, we might be in- 

 duced to call " earthy talc" (which, however, cannot be 

 recognised by us till the presence of magnesia in it is 

 proved), is certainly nothing more than a modification of 

 mica, which, in its usual state, appears hai'd and foliated, 

 but here very soft and scaly. Small pieces of crystallised 

 quartz, rock-crystals, and topazes ai'e found embedded in it. 



2. This soft mass further consists of little round pieces 

 of a snow-white friable lithomarge, which is faintly glimmer- 

 ing between fine scaly and pulverulent soils, adheres to 

 the tongue, is fine and greasy to the touch, and light. In 

 it there is ironglance, crystallised in small six-sided tables, 

 and topazes in still greater proportion. 



3. This lithomarge in the form of small blunt-edged 

 pieces often adopts a yellowish, then a light, and, at last, 

 a very dark brown colour, being entirely impregnated with 

 iron-ochre. There are in it still more little six-sided tables 

 of ironglance than in the white lithomarge. 



It is remarkable that the topaz, the euklase, and the 

 quartz crystals in this formation are always found detached, 

 and very often in fragments ; but it would be a great mis- 

 take to infer from this, that the abovementioned fossils are 

 in a secondary repository. If we compare the occurrence 

 of the softened mass of mica (or lithomarge) at Capao and 

 Lana, with the more solid, though still pretty soft, varieties 

 of mica, at Joze Correa and Chapada, to the south of the 

 former places, and of the Morro, near Villa Rica, we must 

 be convinced, that both are quite similar in their origin and 

 age, and have only undergone a modification with respect 

 to their greater or less solidity. As we believe that every 

 considerable repository of porcelain earth, on and in gneiss 

 and granite, is an original formation, so we are convinced 

 that this repository of mica (if we may use this expression) 



