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326 MINERAL RESOURCES, 1914----PART II.
SAPPHIRE
IOWA.
The discovery of a sapphire on the shore of Lake Okoboji, Dickinson County, Iowa, is described by G. A. Muilenburg.1
This sapphire was found in the gravel along the lake shore by Mr.
Muilenburg in 1912. It is described as resembling a piece of blue
bottle glass worn round and smooth by attrition. Examination showed it
to be a sapphire of good quality, and the stone was later cut into a
gem weighing If carats. It is stated to be the cornflower blue variety,
with a good, velvety luster. This gem was probably transported to the
Lake Okoboji region by ice during the glacial period along with a large
variety of other minerals and rocks. Its original home can only be
guessed at, and Mr. Muilenburg suggests possibly either the Yogo region
of Fergus County, Mont., or some unknown area to the north in Canada.
MONTANA.
Mining
for sapphires was carried on at several localities in Montana, the
principal operations being in Fergus County, where the so-called Yogo
blue gems are mined. The only mine in operation there was that of the
New Mine Sapphire Syndicate, of London, and this company closed down at
the beginning of August after the opening of the war in Europe. The
mine of the Yogo American Sapphire Co. was purchased by the New Mine
Sapphire Syndicate, and for several months preceding this deal the Yogo
American mine had been closed.
Operations
for the variegated sapphires in Granite and Deerlodge counties
consisted of placer work by several smaller producers. The principal
yield from these localities is in sapphire suitable for mechanical
purposes, such as meter bearings and watch jewels. Large deposits of
these sapphires occur along Dry Cottonwood Creek, in Deerlodge County;
along the West Fork of Rock Creek, in Granite County; and along
Missouri River, to the north and northeast of Helena. These deposits
could be made to meet the demands of the American trade arising from
the present decreased imports of foreign materials. The small cull
sapphires from the Yogo mine are used in the higher grade of watch
jewels, and already a shortage of this quality has arisen.
SPODUMENE.
CALIFORNIA.
Mining
at the Pala Chief gem mine, near Pala, Cal., resulted in a production
of about 20 pounds of fine gem spodumene crystals, along with a
quantity of gem tourmaline. The spodumene occurs in magnificent
crystals of pink to lilac and violet colors, with beautiful
transparency through the whole crystal. Some crystals are colorless in
part or throughout. The larger crystals measure several inches in
length, 3 or 4 inches in width, and half an inch to 1 inch in
thickness. Among the larger crystals that have been found in this mine
is one over 11 inches in length and another weighing 47-1/2 ounces.
i Iowa Acad. Sci. Proc, vol. 21, p. 203, 1914.
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