LEAD. 153 



Composition. Pb0 3 C=: Carbon dioxide 16*5, lead oxide 

 83*5 = 100. B.B. decrepitates, fuses, and with care on char- 

 coal affords a globule of lead. Effervesces in dilute nitric 

 acid. 



Diff. Like anglesite, distinguished from most of the spe- 

 cies it resembles by its specific gravity and yielding lead 

 when heated. From anglesite it differs in giving lead alone 

 before the blowpipe, as well as by its solution and efferves- 

 cence with nitric acid, and its less glassy lustre. 



Obs. Associated usually with galena. Leadhills, Wan- 

 lockhead, and Cornwall have afforded splendid crystalliza- 

 tions ; also Linares, in Spain, and other lead mines on the 

 continent of Europe. 



In the United States, handsome specimens are obtained 

 at Austin's Mines, Wythe County, Virginia, and at King's 

 Mine, in Davidson's County, North Carolina ; at the latter 

 place it has been worked for lead, and it is associated with 

 native silver and pyromorphite. Perkiomen and Phcenix- 

 ville, Penn., afford good crystals. It occurs also at " Vallee's 

 Diggings," Jefferson County, Missouri, and other mines, in 

 that State ; at Brigham's Mine, near the Blue Mounds, 

 Wisconsin, partly in stalactites ; at " Deep Diggings," in 

 crystals ; and at other places, both massive and in fine 

 crystallizations. 



When abundant, this ore is wrought for lead. Large 

 quantities occur about the mines of the Mississippi Valley. 

 It was formerly buried up in the rubbish as useless, but it 

 has since been collected and smelted. It is an exceedingly 

 rich ore, affording in the pure state 75 per cent, of lead. 



Carbonate of lead is the " white lead " of commerce, so 

 extensively used as a paint. The material for this purpose 

 is, however, artificially made. 



Phosgenite or Corneous Lead. A chloro-carbonate of lead, occurring 

 in whitish adamantine crystals. H. =2-75-4. G. =6-631. Composi- 

 tion, Pb0 3 C+PbCla. From Derbyshire and Germany. 



Hydrocerussite. Hydrous lead carbonate. From Sweden. 



Ganomalite is a white lead-manganese silicate, affording 34 89 per 

 cent, of lead oxide. From Sweden. Hyalotecite is a lead-barium-lime 

 silicate. Both are from Longban, Sweden. 



General Remarks. — The lead of commerce is derived almost wholly 

 from the sulphide of lead or galenite, the localities of which have 

 already been mentioned. In some mining regions, the carbonate and 

 sulphate are abundant. 



The lead mines of the Central United States afforded in 1826, 1,770 

 tons ; in 1842, 17,340 tons ; and of late years, 12,000 to 15,000 tons. 



