Experiments on American and Foreign Building Stones. 5 
I have also found one very white specimen in which the insoluble | 
matter was only 0-4 per cent., but even from the solution of this, 
ammonia threw down aslight brownish precipitate of oxydof iron, 
A specimen of the blue vein variety showed the following “i 
characters :—Its specific gravity was 2°708. 1218-4 grains pulver- 
ized and carefully washed, afforded a residue of 5:5 grains of iron 
pyrites (and an inappreciable quantity of adhering silica,) equal 
to 0:45 per cent. 100 grains treated with strong acetic acid, lost 
73°7 percent. Strong boiling nitric acid applied to the insoluble 
residue dissolved the pyrites, and the sulphuric acid thence pro- 
duced was precipitated with chlorid of barium, giving 1:62 
grains, equivalent to 0:42 grains of iron pyrites, agreeing very 
nearly with the mechanical analysis. a, 
The acetate was dried up, converted into carbonate and then — 
redissolved and precipitated with oxalate of ammonia, to separate 
the lime, after which ammonio-phosphate of soda threw down of _ 
phosphate of magnesia 1:3 grains, equivalent to 0-47 grain of. 
magnesia, or to 0-97 grains of carbonate of magnesia. From this 
it should seem that the sample was composed of ae 
Carbonate of lime, : ; ‘ : 72:73 - 
Carbonate of magnesia, : ; : 0:97 2 oil 
Sulphuret of iron, 4 ; ‘ : 0:42 7 : 
Insoluble silicates, : ; : ; 25:88 
100- 
_ Asthe pyrites is one of the chief coloring matters of the dark 
Veins, it is evidently very variably distributed through the stone. 
The crystals of sulphuret are mostly small, but easily detected, 
by the naked eye. - 
On breaking a weathered portion of the pyritous vein it is often 
found penetrated from one to two or three inches by the apes 
Ol- 
matter (peroxyd of iron). On the interior parts of the disc 
