DIAMONDS IN ARKANSAS MISER AND ROSS 269 



How much deeper the diamonds may lie is not known, but they 

 probably extend to depths much greater than that to which mining 

 can be carried. 



The yield of diamonds in carats per load of diamond-bearing 

 material differs at different places in the mines and also at different 

 depths. This yield, as it has been determined from the great amount 

 of work at one mine, is 1 carat for 8 loads (16 cubic feet) of diamond- 

 bearing material. In South Africa the yield of diamonds ranges 

 from 6 to 42 carats from 100 loads. 



Most of the diamonds from the Ozark, Mauney, and Arkansas 

 mines have been obtained within the areas in which the volcanic 

 breccia is exposed. Austin Q. Millar, one of the operators, states that 

 the soft, decomposed peridotite overlying the "hardebank" (massive 

 intrusive peridotite) in the north part of the Mauney mine is nearly 

 or entirely barren of diamonds, and that the soft blue, somewhat 

 banded earth (altered peridotite tuff) that covers a small area on 

 the Ozark mine is barren of diamonds. 



The diamonds have probably been concentrated on and near the 

 surface by weathering and erosion. The great amount of erosion 

 that the peridotite has undergone has removed from the outcrop of 

 the peridotite much of the clay and other minerals having a low 

 specific gravity leaving perhaps most of the diamonds and other 

 heavier minerals. The heavier minerals thus concentrated are in 

 the black ground. Mr. Miser has shown, by panning samples of 

 black ground and of the underlying green and blue grounds, that the 

 quantity of heavier minerals to the cubic foot is many times greater 

 in the black ground than in the underlying material. The supposi- 

 tion that there has been a surficial concentration of diamonds is also 

 apparently supported by the results of washing done by the Ozark 

 Diamond Mines Corporation, which obtained a larger yield of dia- 

 monds from surface material than from the underlying disintegrated 

 rock. 



The number of diamonds that have been found near Murf reesboro, 

 Ark., since their discovery in 1906 is only known in part, for the 

 mining companies have withheld from publication the figures show- 

 ing complete production. So far as the authors know, however, the 

 output to date amounts to at least 10,000 diamonds. 



Most of the diamonds from the mines near Murfreesboro have been 

 held by the mining companies, though some uncut stones have been 

 sold. The first cut stones were offered for sale in 1921 by Tiffany 

 & Co., of New York City, and by the Chas. S. Stifft Co., of Little 

 Rock, Ark. 



The diamonds that have been found range in weight from a very 

 small fraction of a carat to many carats. Some are so small that 

 250 of them would be required to weigh 1 carat. The largest 



