Tin.—The Mines of Beariz.
Fortunately for the present proprietary of the Beariz Mines, the late owners possessed considerable technical knowledge; and if the property was not worked extensively by them, the work was prosecuted on right lines. They overhauled the Roman shafts and put in new galleries; and at a time when the standard price of metallic tin was £153 a ton the mine returned the owners a handsome profit. Some years ago, when the mines were reopened and actively exploited, a large number of hands were engaged; and although the ore had to be carted by road to Vigo, large profits were made. Gradually the price of tin dropped, and the profits shrank until operations could only be conducted at a loss. Then work was suspended. Since 1878 the Beariz Mines have remained idle, save for the persistence of the “Tributors,” who have continued to make a livelihood by washing alluvials.
The three leases that comprise the Beariz group are entitled the “Esperanza,” the “Federico,” and the “Elena,” and together they have an area of 450 English acres of tin-bearing ground. Since the mines were closed down, the railway has been constructed from the port of Vigo to within twenty miles of the property, and the roads between Beariz and the railroad are well made and in excellent repair. Señor S. J. Bárris, who was requested to inspect the properties and report upon them by the intending purchasers, spent several weeks at Beariz ascertaining the dimension of the lodes, estimating the extent and value of the alluvial, and making assays. He traced four distinct lodes on the “Federico” property, three on the “Esperanza,” and two on the “Elena,” and his tests proved that the whole of these nine lodes carried rich oxide of tin (cassiterite), averaging thirty per cent. of the mineral. “I am well aware,” he wrote, in communicating the results of his examination, “that the average will appear to be very high, but I would point out that this is a very exceptional property; in fact, I have inspected almost all the known tin properties in Spain, and I can say with confidence that, taking into consideration the numerous lodes and the very rich alluvial deposits, these Beariz Tin Mines are one of the richest, if not the richest, mining properties I have ever seen.”
Worked as a quartz mine, as it was worked by the Ancients, the owners possess in Beariz an asset of proved value, but the property is rendered the more valuable by the fact that the lodes represent only one portion of its assets. For, in addition to the quartz lodes, the greater portion of the 450 acres is composed of tin-bearing ground, almost every yard of which will pay to work. On one side of the hill a large number of boulders are present in the alluvial, which reduces its value; but the major portion of the area is exceptionally free from unbeatable material, and consists entirely of tiniferous deposits. Tin is found in the decomposed granite, which is so soft that it can be worked by pick and shovels. The upper alluvial is about five feet in thickness; but the depth of the granitic formation, which is very rich in tin, has not yet been ascertained. It was for this reason that Señor Alfred Lasala, the leading mining engineer of Orense, reported that it is almost impossible to cubicate the quantity of tin ore in these concessions; but he added in his report that “in every shaft and every trench, cutting, or outcrop, from the highest point down to the bed of the river Beariz, which runs at a great depth below the workings, the tin ore is found in remarkable abundance.” Señor Lasala describes the formation of the Beariz tin deposit as tiniferous granite, concentrated in great masses of tin mineral, which is intersected by cross lodes of tiniferous, quartz veins, or stringers, containing the metal in great quantity. Two samples of earth, that had been washed to remove the mica, tourmaline, and other principal elements of crystalline formation that are present in the ore, assayed 62 per cent. and 81 per cent. of tin respectively; and Señor Bárris estimates that every ton of tin ore, after being properly concentrated, will assay from 62 to 65 per cent. black tin.
The upper alluvials contain a smaller percentage of tin than is found in the lower strata, a fact which is explained by the laws of specific gravity, and by the attention that has been devoted to the surface ground in times past. The granitic formation, which is practically virgin ground, is computed to be hundreds of feet in depth, and there is enough of it on the Beariz property to employ all the energies of the company for fifty years to come. The whole of this formation is traversed by innumerable veins of quartz, containing from 15 to 20 per cent. of tin, which will add enormously to the value of the output.