B.S, Burton—Contributions to Mineralogy. 37 
No. 1, gave 1:34 pr. ct. insoluble residue, and No, 2, 1°72 pr. 
ct. which have been deducted from the above. The ratio of dus 
combined equivalents of the lead, silver and copper to the an- 
timony and sulphur is as 0°50 : 0°24 : 1:19 or very nearly 2:1: 5, 
giving the formula 2(Pb, Ag, Cu)S+8bS,. This corresponds 
to the formula of Jamesonite, of which it seems to form an 
argentiferous variety. The content of silver may indicate its 
ether relation to Brogniardite, an antimonial sulphuret of 
ead and silver of like atomic proportions but containing a 
much larger amount of silver than the Nevada mineral. For 
the analyses the mineral was selected with great care, and it 
appeared perfectly homogeneous. 
Ill. Argentiferous Tetrahedrite. 
- This mineral was one of a number presented to the metallur- 
gical museum from the De Soto Mine, Star City, Nevada. It 
occurs in compact masses of a light gray color and is associated 
with quartz, zinc blende and pyrites. It is readily selected en- 
tirely free from impurities. Specific gravity 500. On exam- 
ination it gave the pyrognostic characters of tetrahedrite, and 
and a nitrogen bulb tube was also added to the absorption ap- 
paratus as in the examination of Jamesonite. After the chlo- 
found by use of the boat that a more perfect decomposition 
was effected than with the bulb reduction tube, and as it is 
