270 ANNUAL. REPORT SMITHSONIAN INSTITUTION, 1923 



diamond, which was found in the Arkansas mine in the summer of 

 1924, weighed 40.23 carats; one weighing 20.25 carats was found in 

 the Arkansas mine in September, 1921, and one weighing 17.86 carats 

 was found in the same mine in May, 1917. The average weight of 

 the 3,000 diamonds that had been produced by the Arkansas mine at 

 the end of 1920 was about 0.4 carat, but the average weight of the 

 diamonds that make up the entire product of all the mines is 

 probably between 0.3 and 0.4 carat. 



Most of the diamonds are white, brown, or yellow. According 

 to Kunz and Washington, there is a large proportion of white 

 stones, most of them of a high grade in color, brilliancy, and freedom 

 from flaws. These authors also say that many of the stones are as 

 fine as any that have been found elsewhere, and that some of the 

 yellow ones are of exceptional quality and color. In describing 

 several yellow, brown, and white stones from the Arkansas mine 

 Kunz says : " These are absolutely perfect and are equal to the finest 

 stones found at the Jagersfontein mine, or that were ever found in 

 India." 



Mr. Millar states that the white stones comprise 40 per cent of 

 the mine run yield from the Mauney and Ozark mines, that the yel- 

 low stones comprise 22 per cent, the brown stones 37 per cent, and 

 bort 1 per cent. Stones having a blue or pink tinge have been found 

 and occasionally a " frosted " or etched white stone is found. Most 

 of the diamonds are crystals, and the most common forms are 

 trisoctahedrons and hexoctahedrons, though some octahedrons and 

 dodecahedrons are found. Crystals with sharp angular faces are 

 rare; rounded surfaces greatly predominate. Fragments and frac- 

 tures are much more numerous among stones recovered from surface 

 material than they are in stones taken from slight depths in the 

 volcanic ground. 



The diamonds shown on Plate 2, Figure 1, are all crystals and are 

 described by W. T. Schaller as follows : 



The crystals seem to be rounded and distorted hexoctahedrons; the bound- 

 ing faces are not typical crystal faces but are end forms toward which the 

 curved faces tend. 



Crystal No. 1: Slightly smoky or brownish in color; probably a flattened 

 and distorted octahedron or hexoctahedron with possibly additional forms. 

 Several of the rounded faces have parallel octahedral-like "etch hills" or 

 " ridges " on them. 



Crystals Nos. 2 and 3 : Colorless ; probably distorted flattened* hexoctahe- 

 drons. 



Crystal No. 4: Brownish; elongated crystal with ends not complete; a 

 different phase of distortion. 



Crystal No. 5: Yellow; very little distorted; essentially a rounded octahe- 

 dron, the octahedral faces being replaced by the rounded faces of a hexoctahe- 

 dron. Shows several solution " pits," one quite deep, in the position of the cube. 



