Asbestos, Its production and use / With some account of the asbestos mines of Canada

by Robert H. Jones

As a general rule, however, the surface veins at Thetford are nearly as pure as those lying deeper in the rock, the reason being that the surface is mostly naked rock only scantily clothed with vegetable mould, moss, or other foreign element, contact with which deteriorates, by discolouring, the fibre, as is found to be the case in a very marked degree in the mines next to be described.

It is a peculiarity of the veins of asbestos that they are never continuous. They vary very much in size, and, in precisely the same way as other mineral veins, they are affected by faults or slides, which not infrequently cut off completely a valuable working face. Where this occurs the slicken-sided character is very marked.

Sheets, also, of imperfect or immature asbestos, having a long coarse woody fibre, are frequently to be seen lying all along the sides of the fault; but, although there is a good deal of this, the general quality of the produce of all the Thetford mines is excellent. The fibre is fine and of a smooth silky texture, very easily worked. The veins are mostly, especially in the lower cuttings, more free from impurities than those of Coleraine.

No steam power is at present used in this district, the whole of the proprietors at present continuing to rely upon hand labour; the Boston Company are, however, as just mentioned, now seriously turning their attention that way, with a view of increasing their output.

The Thetford mine-owners are one and all kind and hospitable men, always ready to give every information and to facilitate an inspection of their works by anyone who will take the trouble to visit them; a trouble which I always found very amply repaid by the courtesy with which I was received, and the candour and obliging readiness with which all my inquiries were immediately answered.

The workers in the mines here are mostly resident on the spot, sufficient accommodation having been provided for them in the immediate neighbourhood of the mines; the proprietors, who appear to act with a liberal consideration towards their men, deeming it incumbent on themselves to look after their welfare; and they find their account in so doing, in not running short of hands at critical times.

The practice at Thetford is to close down entirely for the winter months, it not having yet been found advantageous, in view of the limited market, coupled with the difficulty of outdoor quarrywork, to encounter the extra expense of working at this season. Some of the owners, Messrs. King in especial, being largely interested in the lumber trade, to which they devote themselves in the winter, are able to find plenty of employment at that season for their men and others, who then go off into the woods.

At Thetford, as elsewhere, great mistakes, arising mainly from inexperience and want of the knowledge now possessed, were made when the mines were first opened up, which will inevitably entail serious loss in the future; as an instance, much valuable ground is now seen to be covered up by the dumps, which will unquestionably have to be moved presently when the land is wanted for working.

The same want of foresight, for which there was less excuse with the Thetford experience to guide them, will inevitably cause trouble in the near future at Black Lake, on the property of the Anglo-Canadian Company, even to a more serious extent. The parties who first opened up the ground here evidently knew what they were about, but their immediate successors, being destitute of all practical mining knowledge, have, by their neglect of professional assistance, committed such errors of judgment as will presently occasion very serious expense to the company. At their main pit many thousands of tons of waste rock have been dumped on to some of the richest part of the ground, and this must be again moved before that ground can be worked. From the peculiarity of the work, there probably exists no class of mining which so absolutely necessitates the services of a practical mining engineer, in marking out the land in the first instance for mining and dumping, as that for asbestos does.

The cost of extraction varies in different localities, depending mainly on the mass of barren rock to be encountered and removed. At Thetford the cost may be put at from $20 to $25 per ton, the latter probably being nearer the average. On the Anglo-Canadian Company's property at Black Lake it is a more serious matter. There the quantity of barren overlying rock and earth is enormous, and detracts immensely from the value of the mines. The minimum cost here is $28.