43

to the one analysed. Robertson stated that the hydromagnesite forms
hummocks in a low, swampy depression, ‘‘which are constantly rising higher
and higher and now form mounds 5 to 8 feet above the swamp level.” He
concluded that carbonated swamp waters obtained magnesium carbonate
from underlying soft magnesium - rock and that the process of deposition was
such as to cause the material to “grow up” from below.

Young points out that there is no evidence of magnesium bedrock
directly underlying the Atlin deposits, that there may be 200 feet of uncon-
solidated drift between them and bedrock. He believes the earths were
deposited in ponds by concentration due to evaporation, by the loss of
carbon dioxide, or through some other cause. He combats the spring
hypothesis vigorously, although stating that the ponds presumably receive
their water by underground ways.

The writer believes that in Atlin as in the Cariboo-Clinton areas, the
hydromagnesites were carried to their present sites in solution by under-
ground waters and were not transported either mechanically or in solution
by waters flowing over the surface. Precipitation occurred in ponds or on
dry land according to the surface conditions existing at the place of emer-
gence of the waters.

COMMERCIAL EXPLOITATION.

No attempt has yet been made to develop these deposits of the Cariboo-
Clinton areas. The information upon tonnage given below is based for the
most part on the examination of borings made with an auger by the writer
in 1919. The outlines of the areas in practically all cases were measured
with a steel tape. K. A. Clark of the Mines Branch determined the appar-
ent specific gravity of the material in its natural state as 1-22. This
makes the weight of a cubic yard of the hydromagnesite as it lies in the
ground, including voids, 2,050 pounds. This factor was employed in cal-
culating tonnage instead of the true specific gravity of hydromagnesite.
The results of the borings made in 1919 necessitate a revision of the tonnage
as estimated in 1918. The final estimates of the amounts of hydromagne-
site of possible commercial value are: at Clinton, 3,000 tons; Meadow lake,
114,000 tons; Watson lake, 23,000 tons; Riske creek, 13,500 tons. ‘These
estimates apply only to the upper white layer of hydromagnesite which in
all cases is low in lime but varies considerably in the percentage of siliceous
impurities (Table II). Austrian magnesites with total impurities ranging
from 5 to about 12 per cent have been extensively used in the dead-burned
form for refractory purposes and, lately, Quebec deposits high in lime have
been used after treatment for the same purpose, so that it is difficult to set
limits to the percentage of impurities that would condemn a hydromagnesite
for commercial purposes.. It is believed that the white’ hydromagnesite
layer, and in places the top of the granulated, will prove to be of commer-
cial value. All of the deposits are soft enough to be excavated by steam
shovel, although it may be difficult to do so without including the lower
more impure layers...

The Clinton and Watson Lake deposits lie from 1 to 2 miles from the
railway, Meadow lake is 16 miles distant by road over easy grades, and
Riske creek 35 miles over very steep grades. Clinton, Watson, and

1Reinecke, L., 4éUndoveloned mineral Tecournrs of the Clinton district,’’ Trans. Can. Min. Inst., vol. XXII
1919, and Bull., Can. Min. Inst., Sept., 1919, p. 942.