Mr.
J. F. Boepple, of Davenport, Iowa, estimates the annual production at
about $2,000,000 worth of pearls for the last eight years in the
Mississippi region, and states that for the Wabash River alone in 1906
it is reported that about $1,000,000 worth were gathered. Mr. Beopple
was the pioneer manufacturer of pearl buttons in the Middle West and
was instrumental in establishing both the pearl-button industry and the
pearl industry.
OCCURRENCE OF DIAMONDS IN ARKANSAS.
By Geokge F. Kunz and Henry S. Washington.
In
Pike County, Ark., there is a small area of peridotite which enjoys the
distinction of being the first locality in North America where diamonds
have been found in place, and not in river gravels or glacial deposits.
In the present paper we purpose to give a brief preliminary account of
the locality, of the history of the recent discovery of the diamonds,
and of their occurrence, reserving fuller details for a subsequent
paper.
The
igneous area, which lies about 2-1/2 miles southeast of Murfrees-boro,
the county seat, just east of the junction of Prairie Creek with Little
Missouri River, was first noticed by W. B. Powell as far back as 1842,
later by C. U. Shepard in 1846, and was subsequently described in
considerable detail by J. C. Branner and R. N. Brackett,0 from whose description, supplemented by our own observations, the following geological and petrographical data are taken.
The
mass of igneous rock forms a small stock, which has cut through massive
Carboniferous sandstones and quartzites, somewhat indistinctly bedded
at rather steep angles. Unconformably overlying these are horizontally
bedded Cretaceous sandstones, themselves overlain by coarse,
post-Tertiary conglomerates, the pebbles of which consist of jasper,
chert, and Hint, and which much resemble some of the Brazilian
cascalhos. A small dike of peridotite cuts the Cretaceous sandstone in
the bed of Prairie Creek, but does not penetrate the conglomerate
above, thus establishing the date of the intrusion as post-Cretaceous
but prior to the deposition of the conglomerates.
The
igneous area itself is roughly elliptical in shape, with a longer
diameter of about 2,400 feet and a shorter of 1,800 feet, the former
lying about northeast-southwest, and the latter at right angles to
this. The northwest edge of the area is marked by a ridge with three
summits, of which the southwestern is composed chiefly of
Carboniferous quartzite, as is part of the northeastern one, while the
central hill is composed of a dense, dark, rather fresh peridotite,
which is split by joints into massive blocks. South and southeast of
this ridge, the summits of which lie from 60 to 80 feet above its base,
the surface slopes gently down toward the cotton-planted bottom lands
on the left bank of Little Missouri River. This portion of the area
consists of very much decomposed peridotite, covered in places by a
thin stratum of soil and many pebbles derived from the post-Tertiary
conglomerate. There is little evidence of alteration of the surrounding
sandstones by the igneous intrusion, and, judging from its form and
from the pe-trographic character of the rock, the stock appears to be
the neck of a small volcano, the upper part of which has been removed
by erosion.
aBranner and Brackett, Am. Jour. Sol., vol. 38, 1889, p. 50, and Ann. Rept. Geol. Survey Arkansas or 1890, vol. 2, 1891, p. 377.
