"Grain"
instead of "Carat." Another set would be stamped in milligrams, the
regular milligram weight with the pearl fraction above it, and they
could even be made round so as better to designate the pearl.
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 :
