ANALYSIS OF SOME STEATITES. 171 



external characters were classed together. But the pierre Bildstein coq- 

 de lard, or speckstein, which in some respect may be con- **'°^ '^oxm. 

 sidered as the prototype of the species, having been analysed 

 by Klaproth, and no magnesia found in it, has changed the 

 opinions of mineralogists on this subject, and led them to 

 wish, that some of these substances should be analysed anew. 



With a view to remove this uncertainty, Mr. Haiiy gave Three varieties 

 me three varieties of talc, that I might make a comparative 

 analysis of them. 



The first of these is termed in Hady's Mineralogy lami- laminar talc; 

 nftr talc. It is of a greenish white colour when seen in the 

 mass, very smooth to the touch, and divides into exceedingly 

 -;thin, flexible laminae of a silvery white. 



The second is called in the same work talc glaphique, bild;tein. 

 because it is employed in sculpture ; but commonly pierre 

 de lard. It is the bildstein of the Germans*. This is 

 cotnpact, very greasy to the touch, and of a colour varying 

 between graj'', yellowish, and greenish. Its fracture is dull, 

 uneven, and at the same time scaly. 



Of this species Mr. Haiiy sent me two specimens; one 

 of a yellowish white, from a broken Chinese image; and 

 -the other of a light rose colour, but in every other respect 

 perfectly similar to the preceding specimen. 



4na1ysis of the flexible laminar talc. Laminar talc 



1. I calcined in a strong fire a hundred parts of this calcined j 

 stone. By this operation it acquired a yellow colour, with 



a light rosy tint, was depiived of its flexibility, and lost six 

 parts of its weight. Its taminse being thus rendered very 

 fragile, 1 could easily reduce it to powder. 



2. The hundred parts thus calcined I heated with tv/ice heated with 

 their weight of caustic potash. The mixture did not melt; potash; 

 but its tumefaction indicated, that a combination between 



the substances had taken place. 



3. The mixture diluted with water was afterward dis- ^I'^ated wi'h 

 solved in muriatic acid, and evaporated to dryness in a gen- '""" "^ ^^ 

 tie heat. Towaid the end of the operation the liquor 

 formed a jelly. 



4. The residuum, being lixiviated with distilled water, lixiviated; 



• Agalm:tolite of Klaproth, pagodite of Napione, iteatits prgodite of 

 JBrongi;iart. Tr, 



left 



