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Analysis of' Pyrophyllite, a Nexc Mineral. By M. R. Her- 

 mann of ISIoscow. 



This mineral occurs in the Uralian Mountains, and is known 

 to mineralogists under the name Radiated Talc. But its rela- 

 tions before the blowpipe are different from those of indurated 

 talc. Heated before the blowpipe, without any re-agent, it di- 

 vides in a fan-shaped manner into a swollen mass, which occu- 

 pies twenty times the space of the original specimen. The 

 pounded mass is quite infusible. If heated in a glass-retort, 

 there condenses, on the upper part of it, a water which does not 

 attack the glass, and which, on evaporation, leaves no silica. 

 Soda dissolves the mineral with effervescence, into a clear yel- 

 low glass. Phosphoric salt dissolves it into a colourless glass, 

 leaving a siliceous skeleton. It acquires a blue colour with so- 

 lution of cobalt. By these characters the mineral is well mark- 

 ed, and is distinguished from talc, particularly by its relations 

 with solution of cobalt, its aqueous contents, and its fan- 

 shaped .splitting by heating. But in order to obtain a more dis- 

 tinct conception of this mineral, I subjected it to analysis. Ac- 

 cording to this, it contains in the 100 parts 



We see from this analysis, that the oxygen of the water 

 amounts to a third, and the oxygen of the silica the double of 

 the oxygen of the bases. The mineral thus analysed, therefore, 

 corresponds to the following formula : — 



M^ Si* + 3AP -f lOH. 



The name Pyrophyllite is given to it on account of its exfo- 

 liation on exposure to heat. 



