Precious Stones 



455 



From George K. Kunz, U. S. Geological Survey 



The Carbon Shown on the Opposite Page as Finally Broken into Pieces for Drills 



I, iff. Inner sides of upper part of the carbon shown as Fig. 2 in the preceding illustration. 

 2. The entire piece of carbon broken into pieces weighing from three to four carats each, the 

 sizes generally used for diamond drills. 



