Geological Report on Asbestos and its Indications, in the Province of Quebec, Canada

by Lucius J. Boyd

The cost of extraction is taken from $20 to $25 per ton; this includes local administrations and all other expenses connected with the mine, and with the adoption of machinery and the use of air-compressed drills the cost of actual mining will be reduced to at least 30 per cent.; so taking an average price of about $70 per ton, a net profit of from £8 to £9, or $45, is obtainable per ton of raw material.

In 1886 the total amount of Asbestos, taken from all the mines, may be estimated at 1,500 tons, and of the amount returned last year (1888), all but 400 tons were from the Quebec province mines, and of these Thetford turned out 2,560 tons, and Black Lake 950, or together three-fourths of the whole out-put. The 400 tons were from Bridgewater, in the province of Ontario, a somewhat different class of mineral, which is generally used in the manufacture of fire-proof roofing.

As regards the indications of Asbestos, it is a general recognised fact, and one that may be depended on, that not alone in Canada, but indeed all other places where Asbestos-bearing serpentine is found, the existence of Asbestos, or "Amianthus," is noticed when the serpentine is exposed, and presents a rusted, sometimes greyish and broken appearance, due to decomposition or weathering, or covered with a thin layer of soil. Small veins of Asbestos are to be seen forming a network on the surface of the rock. If closely examined there may be noticed the indications of a fault which, in the eastern townships of Quebec, has generally a direction of N. 40° E., this fault appearing in all openings where a good show of mineral is to be seen, presenting a wall either in a vertical position or at an angle, which is preferred to be not greater than 30°. From this wall, at a varying distance of from 5 to 20 feet, will be found another, sometimes parallel to, or at an opposite angle; in this latter case, if these walls be worked down, they will be found to either meet, forming a trough-like appearance, or to change their course in a downward direction, leaving only a few feet from each other at the narrowest point, and then diverge to an unlimited depth. In this case their faces will have a slicken appearance, smeared over with thin layers of imperfect Asbestos, or crysotile, now and then compact, fibrous hornblende, up to 24 inches in length, of various colours, and rich deposits of olivine, in rare cases small quantities of "ground ivory" with many other admixtures.

The condition of the serpentine within these walls is greatly distorted, containing many small veins of Asbestos varying from mere threads to 2 and 3 inches in thickness, and sometimes deposits of grains of magnetic iron or magnetite with traces of chromic iron, which in some localities break the continuity of the fibre, veins of rich white crystalline matter (perhaps calcareous) with large deposits of "soapstone," or steatite, associated with "serpentite." Such contorted out-crops are indications of rich veins of Asbestos, which will be found to both increase in quantity and quality the deeper they are worked. And in the case where the walls are parallel and the filling matter in the same contorted condition, it is inevitable, in order to obtain a good fibre, considerable depth should be reached.

The serpentine, which constitute these walls, will also be found to proportionally become more compact, and less associated with impurities, and contain the finest quality and lustre of fibre.

A very interesting phenomenon may be noticed at some of the mines in connection with this contorted matter. It is the transposition of the serpentine into Asbestos fibre, by the action of the atmosphere. This is to be seen on the dumps where the filling matter and cobbed rock is exposed. In one or two cases I have seen large quantities of broken rock changed into fibre after a few years, by atmospherical chemical agencies.

In so many cases I find people are prejudiced from going deeper than a few feet from the surface, as not finding a copious supply of Asbestos there, when good indications are shown they become disheartened.

Therefore, from these practical facts it will be seen that in order to get the best results it is necessary to work at the lowest possible level when a favourable out-crop is shown, as, possibly, working at a high elevation on the out-crop may be a mistake, where a lower point is available.

There are good indications of Asbestos where the serpentine is crossed by quartzose, gneiss, or "traverse dykes," and some valuable finds have been made at the junction with the dioretic rocks.

When the serpentine is found dark in colour, to have a granular appearance, containing many dark grains of, perhaps, felspathic crystals, the Asbestos will be of a dark, dull, translucent lustre, very compact, and easily fluffed to a fine silken fibre. The admixtures of hard and soft serpentine, where not effected by a fault, may sometimes be regarded as a doubtful indication of an immediate find, but if its hardness increases on descending, and colour becomes more uniform, from a light emerald green with a whitish admixture, to a dark olive, and containing numerous small veins of fibre, the conclusions may be considered as favourable to rich deposits of Asbestos.