Having been called upon to make a
close and careful examination of the geological formations
in the eastern townships of Garthby, Wolf’stown,
and Coleraine, situated in the province of Quebec,
Canada, I gave special attention to the distribution
of the Asbestos-bearing rocks (serpentine), which
have been, in my opinion, heretofore only partially
traced. Perhaps this was owing to the difficulties
which had to be encountered from the thick undergrowth
which in many places rendered it almost impossible
to penetrate sufficiently in order to make a true
report as regards the “existence,” “location,”
and “association” of these rocks.
Admirable reports have been written
by R. E. Ellis, LL.D., Dr. Hunt, and others, on the
origin and distribution of the serpentines, and
have been fully discussed and ventilated. Still,
though various opinions have been expressed upon the
subject, they appear to differ in many respects.
I mention these facts as possibly one inexperienced
or unacquainted with the country might consider it
strange that a thorough examination of the Asbestos
properties had not been followed. Yet the causes
I have mentioned above, as well as the difficulties
I had to contend with during the months of heavy snowfall,
lead me to believe that my confreres (geologists)
were disinclined to follow up a correct and actual
prospectus of these valuable serpentinous localities.
Before locating, or going into details
of these classes of rock as a mineral repository,
I intend to treat on the subject as regards their
mode of existence and origin.
Serpentine is diffused under the head
of “metamorphic rocks,” while, in the
widest sense, according to Studor and others, mineral
metamorphism means every change of aggregation, structure,
or chemical condition, which rocks have undergone
subsequently to their deposition and stratification,
or the effects which have been produced by forces other
than gravity and cohesion.
There fall under this definition the
discolouration of the surface of, for instance, black
limestone, by the loss of its carbon, the formation
of brownish red crusts in rocks of limestone, sandstone,
many slatestones, shales, granite, &c., by the decomposition
of compounds of iron, finely disseminated in the mass
of the rock, the change in rocks consequent in the
absorption of water, and the crumbling of many granites
and porphyries into gravel, occasioned by the decomposition
of the mica and felspar.
In its more limited sense the term
“metamorphic” is confined to those changes
of rock which are produced directly or indirectly by
agencies seated in the interior of the earth.
In many cases the mode of change may be explained
by our physical or chemical theories, and may be viewed
as the effects of temperature or of electro-chemical
actions adjoining rocks or connecting communications
with the interior of the earth, also distinctly point
out the seat from which this change proceeds.
In many other cases the metamorphic process itself
remains a mystery, and from the nature of the products
alone do we conclude that such a metamorphic action
has taken place.
Serpentine is generally believed to
have been originally deposited as a sediment, and
to have acquired its present compact crystalline character
through the subsequent action of various chemical,
or mechanical, agencies. It is known to be a
hydrated silicate of magnesia with about equal
parts of silica and magnesia, and contains 12 per cent.
of water with varying proportions of iron, chromium
manganese, alumina and lime, has a specific gravity
of 2.7, and weighs about 169 lbs. to the cubic foot.
It is found both in a soft and very compact state,
of a waxy lustre, with many different shades of beautiful
green which give it a mottled appearance like a serpent,
hence the origin of its name “serpentine,”
or ophite. It is called “ranocchia”
by the Italians, from the appearance it bears to the
“frog,” and, on account of its susceptibility
to a high polish, is greatly valued as a marble for
interior ornamental purposes, more than exterior, as
it weathers rapidly. In Galway, Ireland, it is
found in large quantities, and called “serpentinous
marble,” or “ophi-calcite.”
It is also to be found in other parts of the world,
as in the Pyrénées, Alps of Dauphing, Mount St. Gothard,
Italy, Sweden, Ural Mountains, Silesia, New South Wales,
Savoy, Corsica, Cornwall, Scotland, and other places
too numerous to mention; but in Canada the finest
and most crystalline serpentine is to be found forming
great belts of over 100 miles long and several thousand
feet in breadth. There it associates with the
dioretic, or volcanic, rocks, and is, according to
Dr. Ells, without any doubt, “An alteration
product of a dioretic rock rich in olivine.”
It is sometimes very difficult to distinguish the
mineral constituents in many of the metamorphic rocks,
but diorite is always considered to be composed chiefly
of felspar and hornblende, which composition enters
largely into the serpentines. Actinolite,
tremolite, &c., and many other minerals, are sometimes
found associating with it.
There are many valuable properties
attributed to serpentine, and I am of opinion that
the time is not far distant when it will be commercially
considered an invaluable substance, and this on account
of its refractory properties. I may also mention
that it can be extensively used in the manufacture
of crucibles, &c. Its soft and unctuous qualities
(especially where it is found associated with “steatite,”
or “soapstone,” which is often to be seen
in large quantities) renders it easy to be worked,
and, if reduced to a powder, could be moulded in bricks
which the most intense heat will not affect. One
of the chief properties it contains, and one which
the serpentine of Lower Canada is so famous for, is
the Asbestos, crysotile, or fibrous serpentine.
This valuable and important mineral product is found
in paying quantities only at certain points in the
extensive serpentine reefs, and was first mined as
an article of commerce in Canada in 1878, and has now
become a regular and rapidly-developing industry.
On account of its incombustible and
indestructible qualities, is extensively used in steam,
hydraulic, and electrical machinery. It has been
adopted by the Admiralty for engine packing, in Her
Majesty’s war-ships. It is spun into six-fold
yarn, with a tensile strength of 40 lbs. and upwards,
is manufactured into cloth, as clothing for firemen,
and covering hose-pipes, in fire brigades, and also
engine purposes, as well as drop-curtains, and general
stage scenery, and is employed by the principal railway
and steamship companies, collieries, ironworks and
all classes of factories, and, in the manufacture
of the new Asbestos grates and stoves, is finding
for itself a large market. Messrs. Bell & Company
of London, who are the largest Asbestos users in the
world, have adopted it in the manufacture of over
50 special purposes in connection with steam engines
and general machinery, and, as a lubricant, Asbestoline
ranks in the first degree.
There have been many mines started
in Canada by people of the farming class, as well
as by companies, and “cotton,” as Asbestos
is locally termed, has been found in large quantities
within a few feet from the surface, in veins from
1/4 to 6 inches and more in length of fibre. In
Italy, Asbestos is found, measuring up to 6 feet, in
fibre, and chemically speaking, there is no difference
between it and Canadian, except that the latter, though
shorter in fibre, is much more compact and crystalline,
and purer in every sense of the word than can be obtained
in Italy, so much so, as I understand, that users of
Italian material have virtually abandoned it for Canadian.
Although I have no doubt but that Italian Asbestos
has its own special purposes.
The greatest depth reached in Canada
is 130 feet in open workings. No timbering or
extensive machinery is used in the manipulation of
the mines, as the “cuts” being
usually in the mountain side afford a natural
drainage, and dumpage.
Having blasted the rock, the first
process of extraction is termed “cobbing,”
which means breaking off the adhering serpentine from
the Asbestos vein, this being manual work done by
boys. The fibre is packed in sacks, each weighing
100 lbs., and in some cases 200 lbs. are shipped by
the local railroad company to Montreal or New York
at something about 10 cents and 20 cents per sack.
Asbestos is sorted into three qualities,
and priced thus:
1st quality, selling at mine $80 to $200, per ton of 2,000 lbnd " " " 60 " 70, " " "
3rd " " " 25 " 50, " " "
Some inferior quality, at a very low
price, is used by the Asbestos Mining and Manufacturing
Company of Quebec.
The workmen are principally French
Canadians belonging to the neighbouring villages,
and the wages paid them are
Miners (without board), $0.90
(3/9) to $1.25 (5/2), per day.
Pickers and cobbers, $0.40
(1/8) " $0.70 (2/11), "
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 pound
to 9 pound, or 45 pound, 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 degrees
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 degrees. 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.
In conclusion I may add that the foregoing
remarks, as regards the indications of this valuable
mineral, are based on my personal geological experience,
and the reliable information of the managers of the
various Asbestos mines in Canada, whose opinions have
greatly aided me in my recent prospection, and I trust
that this pamphlet will not alone be a benefit to
them, but to the Asbestos industry, which I feel assured
will be one of the most prominent in the province of
Quebec.
Lucius J. Boyd,
C.E., F.R.G.S.I.