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1038                              MINERAL RESOURCES, 1912.
The second area was described by A. H. Purdue,1 but prospecting has developed further points of interest. It is 3 miles S. 75° E. of Murfreesboro, in sec. 14, and is held by the American Diamond Mining Co. The exposures of the peridotite and its weathered products are on a steep north hill slope. Prospecting has been car­ried on by shallow pits, trenches, cuts, a shaft, a tunnel, and drill holes. The peridotite exposures occur within an area of 2-1/2 acres, but the drill holes show that this rock is much larger under and near the surface. Dikes extend outward from the mass of peridotite, or large bodies of the country rock are included in it, or probably both conditions exist.
On the property of the Kimberlite Diamond Mining & Washing Co., about one-fourth mile northwest of the American Diamond Mining Co.'s tract, in sec. 14, peridotite has been exposed in pits, trenches, and drdl holes. The apparent form of intrusion, judging from pres­ent exposures, is that of a crescent-shaped dike with a northeast-southwest strike. This dike is at least 700 feet long and possibly 100 feet wide at the surface, but may be found wider after further prospecting.
There are two exposures of peridotite on the Grayson-McCloud Lumber Co.'s tract, about half a mile southwest of the American Diamond Mining Co.'s property. One of these is at the "Black Lick" near the northwest corner of sec. 23 and the other is about 900 feet to the east. Two test pits were made at these places by Mr. Miser, in which the greenish earth was found to retain the original texture of the peridotite. These two exposures may be on the same mass of peridotite. Hand specimens from these pits closely resemble the decomposed peridotite on the American Diamond Mining Co.'s property, in section 14.
The nature of the peridotite and its products from weathering are similar at the four areas discovered. The fresh peridotite is dark-greenish to brownish-black and in places presents a porphyritic tex­ture. Altered phases become rather more greenish with an earthy appearance and grade into greenish and yellowish soil. A dark to black "gumbo" soil results from the presence of vegetable matter. Numerous inclusions occur in the peridotite, among which black shale, baked by the heat of intrusion, are common.
The rocks of this part of Arkansas are chiefly sedimentary and are of Ordovician, Carboniferous, Cretaceous, and Quaternary age. The Ordovician and Carboniferous rocks, consisting of shales, sand­stones, novaculites, and cherts, outcrop a few miles north of the area in which the peridotite has been found. The peneplaned surface of the Carboniferous rocks is overlain by the Trinity formation, of the Lower Cretaceous, consisting of intercalated beds of marly clay, sand, gravel, and limestone. The Trinity formation is unconformable over­lain by the Bingen sand, of the Upper Cretaceous, consisting of inter­calated beds of gravel, sand, and clay.
The peridotite cuts the Trinity formation, the clays of which were baked to a hard semivitrified rock by the heat of the intrusion, but is overlain by the Bingen sand. At one place, near known peridotite areas, the gravel at the base of the Bingen sand contains altered grains of serpentine and fragments of peridotite. The age of intru-
l A new discovery of peridotite in Arkansas: Econ. Geology, vol. 3,1908, pp. 525-528.