Page:Transactions of the Geological Society, 1st series, vol. 4.djvu/92



Galena is the only lead ore procured in abundance from the veins of this formation; but the white and steel grained ore are occasionally discovered. Silver is contained in the ore in different. proportions, varying from 2 to 42 ounces in the fother of 21 cwts.; but 12 ounces may be considered as the general average. If 7$$\scriptstyle \frac 12$$ or 8 ounces can be extracted the lead is worth refining; though this must in some measure depend on the prices of silver and of refined lead when compared with that of common lead. If the galena is good in quality 4 bings or 32 cwts. of clean ore will yield 20 cwts. of lead; but 4$$\scriptstyle \frac 14$$ bings or 34 cwts. are generally required to produce that weight of metal.

The following is the quantity of lead shipped at the port of Newcastle; average for 6 years previous to