National Geographic : 1903 Dec
PRECIOUS STONES 455 From George F. Kunz, U. S. Geological Survey The Carbon Shown on the Opposite Page as Finally Broken into Pieces for Drills i, ia. 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.