A
full report upon the whole locality, though with special reference to
the American company's property, has lately been prepared by Mr. George
W. Tower, jr. The area of holdings comprises a total of some 500 acres
of land— 300 acres under quartz-claim patent and 500 acres or more
under placer patent. There are 16 patented quartz claims and 1
unpatented, and 13 patented placer claims and 1 unpatented. Some of
the latter were worked for gold ten years ago, and Mr. Tower states
that the first sapphire discoveries were made in cleaning up the
washings of these placers. A full year elapsed before the importance of
this discovery was realized, and the gems were traced to their source
in the dike. Prospecting and tracing out of the dike then went on for
some years, since which time (1001) there has been no further extension
of the dike recognized, and no other dikes have been found in the
vicinity. The main one has been quite thoroughly explored and its
extent determined, as already described.
The
dike runs nearly east and west and cuts almost vertically through
several thousand feet of stratified rocks, horizontal or slightly
inclined, from the Carboniferous down to the basal complex. In width it
varies from 4 to 10 feet, and in texture it is to a large extent soft,
friable, and easily weathered.
Mr.
Tower's report gives details of the workings of both the companies, the
English company east of the crest of Yogo Hill, and the American
company west of it. to and beyond Yogo Creek. Extensive tunnels,
shafts, and levels have been driven, and in the eastern portion also
great open cuttings, besides a number of trial shafts and pits. Mr.
Tower regards the present twofold division of working as unwise and
costly, and strongly advises some form of consolidation and the
concentration of work at the American company's openings at the Fourth
of July claim, on Yogo Creek, the tunnels here to he made the main
thoroughfare for the entire group of workings to the eastward. Here the
creek yields abundant water for washing at all seasons, and the
American company has run over 2.000 feet of tunnels into the dike rock,
besides shafts and cuts to prove its extent. These tunnels. Mr. Tower
advises, should be extended and connected with the openings eastward of
the hill ; thus forming one system and doing away with the expense of
hoisting now involved in the English company's shafts.
The
American company's work has hitherto been chiefly for development,
their only output of gems being those taken out in this process, But
now the extent and richness of the property having been fully
determined, they are erecting a plant for mining en the scale of l00
tons per day. This will quadruple the previous output of both
companies together, and promises to make Montana sapphire mining a very
important factor in American gem production.
The
stones obtained are not of large size. They range from " culls." used
for watch jewels and other mechanical purposes, to gems averaging, when
cut. from half a carat to 2 or 3 carats and rarely up to 5 or 0. As gems they arc brilliant,
free from flaws, and of good color; ranging from light shades to the
rich deep blue of oriental sapphires. The "culls" are produced
abundantly, but not in quantities equal to the demand. They sell
immediately at from $2 to $6 per ounce, and advance orders can
lie had without apparent limit. The Yogo crystals have an advantage for
mechanical uses over East Indian stones in their form, which is largely
short prismatic or rhombohodral with flat basal terminations ; and
hence they need much less cutting for such purposes as watch jewels
and the like.
As
to gems, no very full data can be given ; but the shipment for the
month of November, 1005, from the American company's mines to Xew York
was 1,501 carats in the rough. These are sent for cutting to Amsterdam,
and will
