face
openings and cuts, some of the latter very extensive. Water is carried
from Yogo Creek, ten miles distant, by a ditch and flume, with a
parallel hydraulic pipe line; and a system of sluices extends all along
the company's workings.
"Where
the rock is much decomposed, the hydraulic process is employed largely;
as it becomes harder, power is necessary to break it up. Then the rock
is thrown out in dumps and allowed to disintegrate by exposure to the
weather, as with the African "hard blue." This process requires from a
month to a year, according to the condition of the material. Sometimes
a stream of water is turned on the dumped rock, and the process thus
expedited. When sufficiently decomposed, this material is subjected to
the same washing process as the material naturally disintegrated.
"In
the washing the fine earth is carried away with the water; all hard
lumps remaining are again thrown out on a dump to decompose further;
and the sapphires, after several screenings, are picked out by hand."
An
interesting discovery made in South Africa, in connection with the
process of sorting diamonds by concentrating them on percussion tables,
was that if the tables were covered with thick grease the diamonds, and
even other precious stones, such as rubies, sapphires, and emeralds,
would adhere to the grease and be held, while the valueless
ingredients of the rock would pass by. The grease can be used for this
purpose for only a few hours when it must be scraped off and a new coat
applied. This, however, is a small disadvantage compared with the great
gain afforded by the selective power of the " greaser," as it is called.
Mining
for gems by methods of tunneling, shafts, and other means employed in
deep mine workings is rarely carried on. In the first place, gems do
not often occur in definite veins as do the precious metals, being more
commonly irregularly distributed in pockets through the rock. In the
second place, little really systematic mining of gems is carried on. As
a rule, the occupation is, or has been, a rather desultory one. A find
of a few good stones leads to temporary search and exploration, lasting
for a few years perhaps, then the work proves no longer profitable and
is abandoned until new finds arouse • new hope and revive the industry.
The
element of fortune, good and bad, seems to prevail more largely in the
mining of gems than in even that of the precious metals. In gem-mining,
as in that for gold and silver, great labor and little reward go side
by side with little labor and great reward. Moreover, the dis-
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