Hawor tH. | Lead and Zine. 37 
ried a few hundred feet under the surface. This is the case 
at Leadville, Colo., where was found the most remarkable 
deposit of lead carbonate ever known. The original galena 
from which it was produced was rich in silver, the greater 
part of which was retained in the carbonate ore, and hence 
became a valuable silver ore. 
At Galena only small patches of cerussite have been found, 
and that usually mixed with other secondary ores, particu- 
larly lead sulphate. In some way it received the name of 
‘“‘dry bone,’’ a name indiscriminately applied to lead car- 
bonate, lead sulphate, and zinc carbonate, each of which is 
produced in a similar manner, and, therefore, they are more 
or less intimately associated. ? 
ANGLESITE.—Sulphate of lead, PbSO,. All statements 
made regarding origin and mode of occurrence of cerussite 
likewise may be made about anglesite. It is less abundant 
than cerussite, but is often intimately associated with it, and 
usually the miner and mine operator do not discriminate be- 
tween them. 
These three ores are the only ores that have any consider- 
able value as sources of commercial lead. The total number 
of compounds of lead is very large, rivaling the ores of cop- 
per in number, either of the two producing a larger number 
of minerals than any other of the common metals, save pos- 
sibly iron, and many more than iron does exclusive of the iron 
silicates. This vast number of lead minerals, more than 
seventy-five, usually has no commercial value excepting as 
museum specimens, not because they are not rich in lead, but 
because they occur in such small amounts. Occasionally a 
pocket of some one of them may be found, particularly of the 
oxides, that is sufficient to pay for mining. But it is doubt- 
ful if the entire lot of them produces a tenth of one per cent. 
of the lead of commerce. 
