LEAD 49 



Lead 3871 



Antimony 34-90 



Iron . . 2-96 



Copper 0-21 



Zinc 074 



Sulphur . . . 25-53 



103-05 



Some Jamesonite found near Bampton in Devon contained 15 per cent, of silver. 



9. Bournonite is found near Liskeard in Cornwall, not far from Kingsbridge, and 

 close to Beer Alston in Devonshire. It occurs in many places on the Continent, and is 

 found in both North and South America. Eammelsberg gives it the following com- 

 position : 



Lead 42-54 



Antimony . 2471 



Copper 13-03 



Sulphur 19-72 



100-00 



This mineral may be regarded as a double sulphide of lead and antimony, analogous 

 to the double sulphide of copper and iron. 



The following ores of lead are only of mineralogical interest : 



10. Chloro-carbonate of lead. Cromfordite. Phosgenite. Horn-lead. This ore has a 

 pale yellow colour, is reducible to metallic lead by the agency of soda, and is not 

 altered by the hydrosulphides. Before the blowpipe it melts first into a pale yellow 

 transparent globule, with salt of phosphorus and oxide of copper, and manifests tho 

 presence of chlorine. It is fragile, tender, softer than carbonate of lead, and is some- 

 times almost colourless, with an adamantine lustre. Spec. grav. 6-06. Its constituents, 

 according to Berzelius, are, lead, 25 - 84 ; oxide of lead, 57'07 ; carbonate of lead, 6 - 25 ; 

 chlorine, 8-84; silica, 1-46; water, 0-54, in 100 parts. 



\\.Plattnerite. Super- or Unoxide of lead. A doubtful species. 



12. Linarite. Cupreous sulphate of lead. Found at Leadhills, and in Cumberland. 



13. Susannite. Sulphato-carbonate of lead. Occurs at Leadhills. 



14. Lanarkite. Sulphato-carbonate of lead. Ditto. 



15. Leadhittite. Sulphato-tricarbonate of lead. Ditto. 



16. Caledonite. Cupreous sulphato-carbonate of lead. Ditto. 



17. Vanadinate. Vanadate of lead. 



18. Wulfenite. Molybdate of lead. 



19. Geocronite. Sulphantimonide of lead. 



20. Mendipite. OxycJiloride of lead. 



21. Matlockite, ditto. 



22. Crocoisite. Red lead ore or Chromate of lead. 



23. Vauquelinite. Chromate of lead and copper. 



A few other lead-bearing minerals might have been named, but from their having 

 no commercial value, it has not been thought necessary to do so. 



The ores of lead, which may be represented by galena, or the sulphide of lead, that 

 being the truly commercial variety, are found in rocks of different ages from the 

 granite and clay-slates to the Triassic formations. In the Devonian slate rocks, in 

 the neighbourhood of Liskeard in Cornwall are many most productive lead mines. 

 To the north of Truro is the abandoned lead mine Huel Eose, which from its long 

 celebrity gave its name to the district ; and again to the south of Helstone there have 

 been some valuable workings for lead. These formations of lead ore have all been in 

 the clay-slate, or ' killas ' rocks of Cornwall. In Devonshire many most valuable lead 

 mines have been worked in similar rocks. In these the celebrated mines of Beer 

 Alston on the Tamar existed. With a very few exceptions, but little lead has been 

 discovered in the black slates, the carboniferous series of Devonshire. Some lead 

 ore has, however, been discovered in the New Eed Sandstone and in the slate rocks im- 

 mediately adjoining them near Newton St. Gyres. To the north of the carboniferous 

 rocks of Devonshire we have a renewal of clay-slate rocks, similar in all respects to 

 those which are found near Liskeard in Cornwall ; in these rocks are the once famous 

 argentiferous lead mines of Combe Martin, from which Edward the Black Prince 

 derived an immense revenue. 



Thejead mines of the Mendip Hills, which were at one time very productive, are in 

 the mountain-limestone formation. The lead which is now obtained from the Mendips 

 is smelted, from the refuse slimes and slags left by the old miners. Those of 



VoL.m. E 



