LEAD ORE?. 285 



Vauquelinite is a chromate of lead and copper, of a very dark green 

 or pearly black color, occurring usually in minute irregularly aggregated 

 crystals; also reniform and massive. H=2*5 — 3. Gr = 55 — 5*8. 

 From Siberia and Brazil. It has been found by Dr. Torrey at the lead 

 mine near Sing Sing, in green and brownish-green mammillary concre- 

 tions, and also nearly pulverulent. 



Mendipite. Color white, yellowish or reddish nearly opaque. Luster 

 pearly. Gr=7 — 7*1'. Contains chlorid of lead 38*4, oxyd of lead 61 '6. 

 From Mendip Hills, Somersetshire. Cotunnite is another chlorid of 

 lead, occurring at Vesuvius in white acicular crystals. It contains 745 

 per cent, of lead. 



Corneous lead. A chloro-carbonate of lead, occurring in whitish 

 adamantine crystals. Gr=6 — 6*1. From Derbyshire and Germany. 

 Also said to occur at the Southampton lead mine, Massachusetts. 



Molybdate of lead. In dull-yellow octahedral crystals, and also 

 massive. Luster resinous. Contains molybdic acid 3425, protoxyd 

 of lead 64*42. From Bleiberg and elsewhere in Carinthia ; also Hun- 

 gary. It has been found in small quantities at the Southampton lead 

 mine, Mass., and in fine crystals, at Phenixville, Penn. 



Selenaie of lead. A sulphur-yellow mineral, occurring in small 

 globules, and affording before the blowpipe on charcoal a garlic odor, 

 and finally a globule of lead. 



Vanadinite. A vanadate of lead, occurring in hexagonal prisma 

 like pyromorphite, and also in implanted globules. Color yellow to 

 reddish brown. H=275. Gr=66 — 7*3. From Mexico ; also from 

 Wanlockhead in Dumfriesshire. 



Tungstate of lead. In square octahedrons or prisms. Color green, 

 gray, brown, or red. Luster resinous. H=2*5 — 3. Gr=79 — 8*1. 

 Contains 51 of tungstic acid and 49 of lead. 



Plumbo-rcsinite. In globular forms, having a luster somewhat like 

 gum arabic, and a yellowish or reddish-brown color. H=4 — 4*5. 

 Gr=6*3 — 64. Consists of protoxyd of lead 40-14, alumina 37*00, 

 water 188. From Huelgoet in Brittany, and at a lead mine in Beaujeu ; 

 also from the Missouri mines, with black cobalt. 



GENERAL REMARKS ON LEAD AND ITS ORES. 



The lead of commerce is derived almost wholly from the sulphuret 

 of lead or galena, the localities of which have already been mentioned. 



This ore is reduced usually by heat alone, in a reverberatory furnace. 

 The process consists simply in burning out the sulphur after the ore is 

 picked, pounded and washed. The galena is kept at a heat below that 

 required for its fusion, and air is freely admitted to aid in the combus- 

 tion. The sulphur is driven off, leaving the pure lead, or an oxyd formed 

 in the process which passes to the state of a slag. The latter is heated 

 again with charcoal, which separates the oxygen. A portion of quick- 

 lime is often added to stiffen the slag. In England, the whole ope- 

 ation of a smelting shift takes about 4£ hours, and four periods may 

 be distinguished : — The first fire for roasting the ores, which requires 



What is the source of the lead of commerce ? How is the ore 

 leduced ? 



