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mineral was heated and immersed in it, without damage. The 

 Quincy sienite and true granite will alone bear this test ; the 

 so-called granite, which is truly gneiss, fails under its application. 

 The enduring qualities of this stone being thus demonstrated, it 

 may safely be used in permanent works, where its variegated 

 shades of white and green will long preserve their polish and 

 beauty. 



This mineral has been called Verd-Antique Marble, a name 

 not only incorrect, but conveying a false conception of its value 

 in a technical sense, as verd-antique marble does not resist ex- 

 posure to our atmosphere. The experiments alluded to above, 

 proved that the white portions were not marble, and as these 

 portions resisted chemical agents, nearly as well as serpentine 

 does, I was anxious to learn the composition of the whole. Dr. 

 Brewer kindly furnished the specimens, which he took from the 

 quarry during a recent visit, parts of the collection he has now 

 presented. 



The analytical experiments were first made on the white 

 portion of different masses, and the results established the inter- 

 esting fact, that this part is an anhydrous Carbonate of Magnesia, 

 nearly pure. 



The white part, often highly crystalline, can be separated 

 from the masses only in small fragments. It then presents a 

 milk-white color, is translucent, the cleavage planes having a 

 high lustre. Generally, it contains scaly talc, of a clear green 

 color, or it is blended with a dark green serpentine. 



The selected portions of the white parts were used in the 

 following determinations : — 



100 parts of the powder lose humidity at 212° F. and at 

 450° F. ; the whole loss is 0.08. 100 parts of the dried powder 

 afford 47 parts of carbonic acid, as collected ; the total loss of 

 weight was 48.80 parts. 



100 parts of the dried powder consist of : — 



Carbonic acid 48.80 



Magnesia 45.60 



Talc and a little Silicic Acid . . . 3.60 



Silicate protoxide of Iron . . . . 1.96 



99.96 



