422 G. J. Brush—Compact Anglesite from Arizona. 
by Mr. Samuel T. Tyson, of this laboratory, has confirmed the 
correctness of the first examination. 
ous circular or elliptical lines, as so often seen in agate. The 
bands or layers next the galena are frequently almost black, 
fading from a dark brownish-gray to a light grayish-white at 
the point farthest from the nucleus of galena, and the outer 
sulphuric acid. Four analyses made by this method gave Mr. 
Tyson. 
Dark variety. Light variety. 
r — ——_————{Ss—s --- oor 
I 1 2 
Oxide of lead, 72°53 72°62 72°34 72.53 
Sulphuric acid, 26°43 26°33 26°29 26°28 
Insoluble residue, 0°75 0°73 0.83 0°75 
99°71 99°68 99°46 99°56 
A fire-assay of the light variety yielded Mr. Tyson 0-0578 
per cent silver, 16-87 ounces per ton of 2,000 lbs., while the 
galena was found to contain 27-3 ounces per ton, thus proving 
that a considerable portion of the silver was lost in the process 
of oxidation. The insoluble residue in the dark variety was 
almost black, and a qualitative examination of it showed it to 
be chiefly sulphide of lead, while the residue from the light- 
colored mineral was nearly white and almost entirely insoluble 
im acids, and proved to consist mainly of clay. 
Sheffield Laboratory, New Haven, April, 1873, 
