Sources of Silver.
Strictly speaking, silver mining does not exist as a distinct operation in Great Britain, for it can hardly be said that this country possesses any great quantity of silver ore. Yet we must not disguise or leave unnoticed, in dealing with this subject, the positive fact that silver is found to some extent in our copper and lead mines, principally in the latter; but in no case, as far as we know, have mines been worked for the sake of the silver alone. It is almost always found in conjunction with lead, and it is from that source that we have a good supply of British silver. The average annual yield in the British Isles for some years has been equal to 800,000 ounces—a position in regard to the quantity produced ranking second only to Spain amongst the nations of the world, America, of course, being excepted. Silver is found in a native state, the commonest ore being a sulphuret.
The chief European supplies are derived from Spain, in which country genuine silver ore exists; from Saxony and Prussia, where the ores are principally associated with lead, as in England; and from Austria, where it is for the greater part found mixed with copper. Silver is nearly always to be found in copper and lead mines, but generally in such small quantities that it is rarely worth the trouble and expense of separation.
Considerably more than three-fourths of the whole total supply of silver comes from America; and in fact nearly the whole territory of America is said to be more or less argentiferous. Until lately Mexico carried off the palm, as containing and yielding the largest percentage of silver; but through the discovery of another mine in the United States, at Nevada, of considerable richness, which has yielded enormous supplies, we shall not be far wrong in pronouncing the silver mines in the State of Nevada to be the richest in the whole world. The extensive production of these mines, combined with other causes, has led to a considerable depreciation in the value of silver, and probably this may yet lead to its more extensive employment in the arts and manufactures; and, in the midst of the very general depression of the jewellery trade, any change extending in that direction would be joyfully accepted by the thousands of workmen in the precious metal trades now standing idle. We are told that, since the year 1860, the production of silver has increased from an average yield of eight or nine to fourteen millions per annum, or about 60 per cent.; while, on the other hand, the foreign demand for the metal (formerly largely employed for the currency) has greatly diminished. The rise in cost of silver during the war years and those immediately following necessitated an Act in Great Britain “to amend the law in respect of the standard fineness of silver coins current in the United Kingdom and in other parts of His Majesty’s Dominions.”
The chief sources of supply in the British Isles, according to Professor George Gladstone, are as given below; and as all the silver found in this country is produced from lead ores, the average yield here given must be understood to exist in about that proportion to every ton of lead ore assayed:—Isle of Man, 50 to 60 oz.; Cornwall, about 30 oz.; Devonshire, about 30 oz.; Cardiganshire, 15 to 20 oz.; Montgomeryshire, 15 to 20 oz. Thus, it will be seen the lead ores of the Isle of Man yield the greatest proportion of silver in the British dominions. Silver is also found in the undermentioned counties, in all of which it is produced from lead ore:—Cumberland, Durham, and Northumberland, Denbighshire, Flintshire, and Derbyshire; but the percentage is much smaller than in the preceding cases. Ireland also yields a fair percentage of silver.
The Assay of Silver Ores.