TRAVELS IK BRAZIL. 203 



in any single piece, the true chlorite, which is always 

 distinguished by its decidedly gi-een colour, and the con- 

 siderable proportion of talc earth and iron, and forms in- 

 deed subordinate layers, as well as a component part of the 

 veins and beds of ore in mica-slate, but no immediate 

 constituent part. Vauquelin, in vol, Ivi. p. 59. of the 

 Journal de Phys. (Scherer's Journal de Chem. No. 

 xxxviii. p. 189.) has analysed a piece of white chlorite, 

 from what place is not known, and finding it to contain 

 56 parts silex, 18 argillaceous earth, 6 alkali, 3 lime, 

 4 iron, and 5 loss, he perceived that this fossil was not 

 chlorite, and called it Margariton, on account of its mother 

 of pearl lustre. As the undulating mica accumulated on 

 the rifts of the mica-slate in our possession, to the thick- 

 ness of half an inch, exactly coincides with that described by 

 Vauquelin, this may furnish an additional reason to affirm 

 that Mr. Von Eschwege's " silky shining scales" {loc. cit. 

 p. 17.) are not talc, and much less chlorite. * The mica- 

 slate, formerly known under the name of flexible sand- 

 stone, is distinguished from the common only as the 

 greyish white quartz is the chief constituent, and has a 

 granular structure, whereas the quartz of the mica-slate 

 of the old world is mostly of a compact structure. We 

 however find in Europe varieties of the mica-slate, which 

 resemble the Brazilian. Thus, for instance, in Gastein, 

 in Anlaufthale, in the province of Saltzburg, there occurs 

 in narrow subordhiate beds in common mica-slate, a 

 variety, the quartz of which is also granular, and the mica, 

 fine scaly, and so like the Brazilian in colour, that it 

 might be supposed this variety of the mica-slate had been 

 taken from Mount Itacolumi. Strictly speaking, Mr. 



* See Von Eschwege's Accounts of Portugal, published by Zinken, 

 who (p. 234.) has made well-founded objections against the denomina- 

 tion, chlorite, and confirmed them by its fusibility by the blow-pipe, 

 but erroneously called the fossil, talc. 



