Measures Diamond size. Instead, “carat”
measures diamond weight. One “carat”
equals 200 milligrams, or 20%of a gram.
Not all diamonds of the same carat-weight
appear to be the same size, however.
Apparent size depends upon the shape of the rough stone and precisely how it was cut
and finished. For example, a one-carat diamond that is unusually deep may appear
smaller (looking down from the top) than a better-proportioned, more expertly cut one-
carat stone (see “Cut
Gemstone weight also is expressed in “points:” One carat equals 100 points. So a half-
carat gem is “50 points,” a quarter-carat gem can be described as “25 points.” A gem
greater than one carat can be described in both carats and points, for example as “1.63
carats,” or “one carat, sixty-three points.”
Diamond price is founded on rarity. Obviously, large diamonds are radically more rare than
small ones. Therefore, the price of a diamond that weighs, say, a full carat is dramatically
greater than twice the cost of a similarly graded half- carat diamond.
The combined carat-weight of all the stones in multi-gem jewelry frequently is described in
terms of the total carat weight (TCW) of all combined stones in the piece.
(Don’t confuse “Carat
,” [gemstone weight] with “Karat,” [percent of pure
gold in an alloy]. For example, 24-karat is 100% gold; 12 karat is 50% gold;
other metals comprise the remaining 50% of the alloy.)