ANALYSIS OF SOME STEATITES. jy^ 



putation, and not by direct experiment; for, to whatever 

 heat I exposed the stone, it never lost more than 5 per cent. 



From the analyses here given it follows, that of the Bildstein 

 three varieties of talc here mentioned, two only must con- thtrefore an 

 tinue to he so called; namely the laminar talc, and the 

 compact rose-coloured talc. The third, the speckstein, 

 should be removed to the genus of alkaliniferous stones. 



It is particularly remarkable, that those two varieties, Minerals 

 which most resemble each other, and which have always ^j'^^"gj|j'°,j^^ 

 been classed together, should now be separated by analysis: external cha- 

 which shows, that minerals should never be classed accord- ''^'^^'^f** 

 ing to their external appearance^ since the most striking 

 analogies in this respect are the most deceitful. 



In fact, the speckstein and compact rose-coloured talc 

 have the same softness, the same fineness of particles, the 

 same fracture, nearly the same specific gravity; and cer- 

 tainly, if there were any room to suppose, that one of the 

 three substances ought to be separated from the talc species, 

 we should be more inclined to suppose it the laminai*, than 

 either of the others. 



Note. On this occasion I analysed that species of talc Arau-sis of 

 known by the name of craie de Briam^on, or French chalk, French chalk. 

 and I found it to contain the same principles, and nearly in 

 the same proportions, as the laminar talc, and the compact 

 rose-coloured talc. These proportions were, 



Silex •• 61-25 



Magnesia 26*25 



Water. 6 



Alumine 1 



Oxide of iron 1 



Lime • • • •' 073 



Loss." »«•.»♦•... 3'75 



100 



iV 



