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664 MINERAL RESOURCES, 1913—PART II.
it
served to show in what ways improvements could be made in the mills and
machinery so far used to treat the peridotite. The companies making
the tests have not seen fit to announce the results of their work, but
they kindly allowed examination of their mines and mills at the time of
the writer's visit in July, 1913. Two washing plants were built, one by
the Ozark Diamond Mining Corporation on their holdings at the
northeast side of the original peridotite area, and the other by the
Kimberlite Diamond Mining & Washing Co., on the west side of
Prairie Creek.
The
Ozark Co. operated its washing plant about three months during 1913.
Mr. Warren, the superintendent, estimated that about 5,000 loads of 16
cubic feet of decomposed peridotite from the original area and about
1,000 loads of gumbo and wash gravel from the west foot of Twin Knobs
were washed., The last of this gumbo and gravel were being washed at
the time of the writer's visit, but no diamonds had been found in it.
Several hundred diamonds were recovered in washing the peridotite from
the original area. This peridotite was obtained from an open cut 300
feet long, 15 to 35 feet across, and 8 to 20 feet deep, with tracks
leading to the mill. A quantity of surface material was washed in
sluice boxes with riffles and yielded a larger per cent of diamonds
than the underlying peridotite. Most of the peridotite, even from the
bottom of the open cut, was found to be so decomposed as to be ready
for washing as mined.
The
mill is equipped with a stationary boiler and engine, a trommel
separator feeding an elevator to a large storage bin, sizing screens,
jigs, and a stationary grease plate table. The oversize is passed
through a jaw crusher and then to the storage bin. After necessary
changes have been made in the mill further experiments are to be made
in washing the peridotite.
The
Kimberlite Diamond Mining & Washing Co.'s plant is nearly a mile
from its lease holdings on the original peridotite area. A tram has
been built from the mine at this place to the mill and another tram
will be built to the company's holdings, 3 miles east of Murfreesboro,
if success is met with in prospecting and preliminary washing. The mill
is substantially constructed with a large storage floor. The earth to
be treated will be fed through a revolving screen and into a 10-foot
diamond concentrating pan of South African pat-. tern. It is estimated
that this pan will treat from 100 to 150 loads of 16 cubic feet per
day, reducing 100 tons of earth down to about 1 ton of concentrates.
The concentrates will be further screened and then treated on jigs, and
the final concentrates examined on metal covered tables in a
well-lighted room. Oversize from first screening will be subjected to
further weathering. Tailings will be conveyed by flume to Prairie
Creek. Final equipment of the mill with automatic handling machinery,
grease table, and other improvements will be carried out after the
value of the property is proved.
The
Arkansas Diamond Co. was idle during 1913, but since the writer last
visited the property in 1908 several changes have been made. The
peridotite hills have been stripped of timber and a dozen or more new
pits and shafts have been made, some of which were of value in showing
the depth of decomposition over various parts of the peridotite area.
Weathered peridotite has been scraped off of a small area and washed in
improvised machinery which proved wasteful in operation. A large area
of ground sloping south toward Little
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