Analysis of some Steatites. 137 



nesia, this earth having been found in all of them that have 

 been analysed 5 and in consequence all stones possessing 

 these external characters have been classed together. But 

 the pierre de lard, or speckstein, which in some respect 

 may be considered 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. * j 



To remove this uncertainty, M. Haiiy gave me three va- 

 rieties of talc, that 1 might make a comparative analysis of 

 them.- — The first of these is termed in Haiiy's -Mineralogy 

 laminar talc. It is of a greenish white colour when seen ia 

 the mass, very smooth to the touch, and divides into ex- 

 ceedingly thin flexible laminae of a silvery white. — The 

 second is called in the same work talc glaphique, because it 

 is employed in sculpture; but commonly pierre de JarJ. It 

 is the bildstein of the Germans. This is compact, very 

 greasy to the touch, and of a colour varying between gray, 

 yellowish, and greenish. Its fracture is dull, uneven, and 

 at the same time scaly. — Of this species M. Hatiy 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 speci- 

 men. 



Analysis of Flexible Laminar Talc. 



1. One hundred parts of this stone, calcined in a strong 

 fire, acquired a vellow colour, with a light rosy tint, was 

 deprived of its flexibility, and lost six parts of its weight. 

 Its laminae being thus rendered very fragile, I could easily 

 reduce it to powder. 



2. The hundred parts thus calcined I heated with twice 

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

 but its tumefaction indicated, that a combination between 

 the substances had taken plaee. 



3. The mixture diluted with water was afterwards dis- 

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

 tle heat. Towards the end of the operation the liquor formed 

 f jelly. 



3, 4. The 



