Precious Gem stones production in 1907 Page 37



	PRECIOUS STONES.	803

	thus bringing out the mammillary structure of chalcedony in peculiar wavy markings. In other pieces the color approaches that of chryso-prase, or resembles that seen in certain artificially colored chalcedony. Air. Wightman reports a sale of probably 200 pounds of selected mineral during 1907 by the miners in Globe. After cutting, this blue chrysoprase brings locally from S3 to $10 a piece for the best grades. DIAMOND. UNITED STATES. Arkansas.—The work of testing the Arkansas diamond deposit continues quietly. A brief report on the locality was prepared by Philip F. Schneider" for the Arkansas Bureau of Mines. The latest authoritative information on the Arkansas diamond deposit has been given by Messrs. Kunz and Washington in a paper before the February meeting, 1908, of the American Institute or Mining Engineers in New York. The general geology of the area and the petrography and weathering of the peridotite are described as they were in a paper by the same authors incorporated in this report for 1906. In tests made with a diamond drill the peridotite was proven to depths of 80, 186, and 205 feet. The green and yellow grounds underlying the layer of black, sticky "gumbo" soil were found to extend down 40 feet in places and are estimated to average 20 feet in depth over the area. The outcrop of the peridotite is estimated to cover about 40 acres, though it may be found larger after further exploration. General conditions concerning future work are briefly discussed. Water supply, timber, and coal are available, and labor and transportation facilities can probably be satisfactorily arranged. Some 140 diamonds have been found, with an aggregate weight of about 200 carats. The largest stone weighs less than 6-1/2 carats, though the average size compares favorably with the general run of most of the South African diamonds. There is a large proportion of white stones, many of which are free from flaws and are very brilliant. Some of the yellow diamonds are also of exceptional quality and color. The genuineness of the occurrence of the diamonds in their matrix is reiterated, and the occurrence of one stone embedded in the green ground at a depth of 15 feet is cited to strengthen the conclusion. The quantity of green ground that can be readily washed is large. Portions of the peridotite on the borders of the outcrop are in such hard masses as to indicate that it will not readily decompose. The sludge and cores from the diamond drill tests, however, show a badly altered rock at depth at many places, and suggest that much of the peridotite from depth will readily disintegrate on exposure to the weather. Some fresh hard peridotite will be encountered, as in the South African mines, and will probably have to be treated with a certain amount of crushing. Warning is given against the unscrupulous who will probably claim to have located new peridotite areas "on the same "lead" or "an extension" of the present one. It is pointed out that since this peridotite has the form of a pipe its outcrop will be limited to one place. Even should new areas of this rock be located, and should their nature be proven by an examination of a petrographer, a Schneider, Philip F., A preliminary report on the Arkansas diamond field: Arkansas Bur. Mines, Manufactures and Agriculture.