DR T. THOMSON on Asbestus, Chlorite, and Talc. 381 



It is undoubtedly connected with the mineral to which the 

 name of Nephrite has been given. I subjected to analysis the 

 well known nephrite, found on the shores of lona, and which ap- 

 pears to have formed a part of a limestone-bed in that island, 

 long since wrought out. Its specific gravity is 2.595, and its 

 constituents were found to be, 



Silica, 40.7 



Magnesia, 43.156 



Protoxide of iron, . . 3.528 



Water, 13.200 



100.584 

 This is equivalent to 



6 atoms silica, 

 5 atoms magnesia, 

 0.2 atom protoxide of iron, 

 3^ atoms water. 



Which may be reduced to 



25 atoms silicate of magnesia, 

 1 atom quintosilicate of iron, 

 I6f atoms water. 



While the indurated talc consists of 



25 atoms silicate of magnesia, 

 5 atoms silicate of iron, 

 5 atoms silicate of alumina, 

 6^ atoms water. 



Thus the water in nephrite is just thrice as much as in indu- 



