Page:Transactions of the Natural History Society of Northumberland, Durham, and Newcastle-upon-Tyne 1838 Vol.2.djvu/162

152 No. III.— An Account of the Method of Smelting Lead Ore and Refining Lead, practised in the Mining Districts of Northumberland, Cumberland, and Durham, in the year 1831. By Mr. H.L. P ATTINSON .

R EAD, Oct. 17, 1831.

The total quantity of Lead ore, produced in the northern mining districts annually, is about 70,000 bings, of 8 cwt. avoirdupois each, or 28,000 avoirdupois tons. Nearly the whole of this quantity is Galena, which, on reduction, yields Lead containing from two to twenty-four ounces of silver per fodder of 21 cwt. or 2352 lbs. The other varieties of Lead ore which occur, are Carbonate and Phosphate of Lead, but they are always found in situations near the surface, and in comparatively small quantities.

The Galena is principally cubical, but some veins produce steel- grained, compact, and antimoniated Galena. Cubical and steel-grained Galena are often variously blended together, and every variety is, in most cases, intimately mixed with Spar and Vein Stone, or Rider, as it is provincially called, when brought out of the mines. Each vein contains generally a peculiar, and frequently a distinguishing, species of Spar and Rider. The Spars are Fluate and Carbonate of Lime, Pearl Spar, Sulphate of Barytes, Baryto-calcite, and among them may be included Blende and Iron Pyrites. The Riders differ nearly as much. In some veins they consist of fragments of the adjacent strata, apparently cemented together by interposed spar or ore; and in others, the Rider is a hard and (as the miners term it) burnt, or soft and friable stone, strongly impregnated with iron.

However these substances are intermingled with the ore, they ought to be removed as much as possible in the process of washing, for, except this is done entirely, the residual portion affects the ore, and gives it a peculiar character in the subsequent operation of smelting. The