DIAMOND-BEAEING PEEIDOTITE IN PIKE COUNTY, 



AEKANSAS 1 



By Hugh D. Misek and Clarence S. Ross 

 Geologists, United States Geological Survey 



[With 3 plates] 

 INTRODUCTION 



The diamond mines of Arkansas, which have produced several 

 thousand stones, are the only such mines on the North American 

 continent, though a few diamonds have been found from time to 

 time at other places in the United States and at some places in 

 Canada. 



Most of the diamonds found in North America outside of Arkansas 

 have been obtained from gold placers in the Piedmont region of 

 the Carolinas and Georgia, from placers in the Western States, es- 

 pecially California, and from glacial deposits in regions as widely 

 separated as Nova Scotia and Wisconsin. All these stones were 

 found far from their sources, for placers are composed of stream- 

 transported material and glacial deposits consist of ice-transported 

 rock debris. The material in the placers has been carried from 

 rather well-known regions in which it seems unlikely that rich 

 diamond-bearing rocks occur. The diamonds found in these placers 

 were probably derived from dunite or serpentine, rocks that are 

 related to diamond-bearing peridotites but that contain very few 

 if any diamonds. The diamonds found in the glacial deposits, like 

 the granitic boulders, were carried from their parent ledges in 

 Canada by the continental glaciers that advanced southward into 

 the northern United States. It has therefore been surmised that the 

 rocks at some places in Canada might be rich in diamonds, but if 

 such a diamond deposit exists it is lost in the vast barren lands of 

 the North — more hoplessly lost than the most fanciful "lost gold 

 mine " of our own great West. 



The diamond deposits of the world may be grouped into two 

 principal classes. Those in Brazil, India, and Australia and some 

 of those in Africa are in placers, where the stones have been more 

 or less concentrated by wind and water; but the largest deposits in 



1 Abstracted and reprinted by permission from Economic Geology, vol. 17, December 

 1922. 



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