Intelligence and Miscellaneous Articles. ^2$5 



Warmbrum in Silesia, analysed by MM. G. Rose and Rammels- 

 berg. 



Mica. — M. Beudant has already observed that protogine contains 

 mica : it is of a more or less deep green colour, and has little or no 

 lustre ; by calcination in an open crucible it becomes of a reddish- 

 bronze colour, with brilliant reflexions ; in a close crucible it becomes 

 blackish green. When it is in very thin laminae the action of the 

 air is sufficient to give it a bronze colour, which is a character that 

 may serve to recognize it. Its density is 3*1£7, which ii much 

 greater than that of the micas of granites ; this is unquestionably 

 owing to the large quantity of oxide of iron which it contains. 



It is not crystallized in small transparent scales ; on the contrary, 

 it has the form of small irregular hexagonal prisms, the edges of 

 which are not perpendicular to the bases. 



Before the blowpipe the edges are rounded with difficulty when 

 in small laminae ; with fluxes it indicates iron and manganese, and 

 it dissolves entirely in phosphate of soda. 



It is perfectly acted upon even by hydrochloric acid, and the silica 

 separates in the form of flocculi : the facility with which it is acted 

 upon is probably owing to the great quantity of iron. 



The analysis was performed on the mineral taken from the granite 

 block already mentioned ; it gave — 



Silica 41-22 



Alumina 13-92 



Peroxide of iron 21-31 



Protoxide of iron 5-03 



Protoxide of manganese... 1-09 



Lime' 2-58 



Magnesia 'l-'TO 



Potash 6-05 



Soda 1-40 



Fluorine 1*58 



Water and loss by heat . . 0*90 



99-78 



Talc. — Protogine also contains a substance forming very small 

 contorted laminae inserted among its various minerals, and which is 

 to be regarded as a variety of talc. It has a pearly lustre ; its colour 

 varies from celadon to emerald and pale grayish-green. By calci- 

 nation it acquires sometimes a brownish tint and sometimes a bright 

 wood-brown tint, with golden reflexions ; pure talc becomes very 

 slightly yellowish silver-white. It is not elastic ; its hardness is 

 rather greater than that of talc, even when unmixed with foreign 

 matters ; like talc, it scratches glass after calcination. 



Very thin laminae of this talc, extracted from various specimens 

 of protogine, were tried by the blowpipe; at a very high tempera- 

 ture, as already remarked by Saussure, their edges were rounded 

 without exfoliation, and the fused portion was coloured by iron. 

 Talc, on the contrary, exfoliates without fusing ; this fusibility of 



