The great value of pearls has suggested the making of a gage, called the Kunz gage, by means of which round pearls can be very accurately measured. Pearls of a given weight and perfectly spherical form have been weighed and then measured by this gage, and the theoretical diameters as computed from the measurement of a single pearl are in the majority of instances in exact accord with these actual measurements, the occasional variations in the smaller pearls barely exceeding the thousandth part of an inch. These discrepancies may be due to imperceptible divergencies in sphericity or, possibly, to trifling differences in specific gravity. The following table gives the diameters of round pearls by measurement, from 1⁄16 to 500 grains, in millimeters and inches: Weight Grains Diameter Millimeters Inches 1⁄16 1.3 .0512 ⅛ 1.66 .0653 ¼ 2.09 .0823 ½ 2.65 .1043 ¾ 2.99 .1187 1 3.32 .1307 1¼ 3.60 .1417 1½ 3.80 .1496 1¾ 3.98 .1567 2 4.18 .1645 2¼ 4.32 .1701 2½ 4.47 .1759 2¾ 4.63 .1823 3 4.80 .1889 3¼ 4.88 .1921 3½ 5.01 .1972 3¾ 5.17 .2035 4 5.23 .2058 4¼ 5.44 .2141 5 5.65 .2224 5½ 5.86 .2283 6 6.03 .2374 6½ 6.20 .2442 7 6.36 .2504 8 6.64 .2614 9 6.90 .2716 10 7.15 .2815 11 7.38 .2905 12 7.60 .2992 13 7.81 .3074 14 8.00 .3149 15 8.18 .3220 16 8.36 .3291 17 8.53 .3358 18 8.70 .3425 19 8.86 .3488 20 9.01 .3547 25 9.71 .3823