Weight and Value of Diamonds

The diamond is known in three different molecular states, forming a graduated series that is very remarkable. It is crystallized, crystalline, and amorphous.

The crystallized diamond is the diamond "par excellence;" it is that which, when cut, is used in jewelry.

The crystalline diamond cannot be cut. It bears in commerce the name of "boart," and is reduced to powder for cutting crystallized gems.

The amorphous diamond is of a steel-gray colour and quite opaque. It occurs in sandstone of very old formation, and is found in Bahia, and of late in Mexico. It has no utility when cut, but reduced to powder it is used for polishing diamonds and other gems, and is especially prized by the watchmakers of Switzerland. Its hardness is identical with that of the crystallized diamond; its specific gravity is 3.012 to 3.016. It is not used to so good advantage in proportion to its weight as "boart." It is known in commerce under the name of carbonate, or carbonic diamond.

Crystallized diamonds in their natural state are called "rough diamonds."

The diamond is always sold by weight. The standard of weight for all precious stones is the carat; a name derived, it is said, from the seeds of a pod-bearing plant used in the East to measure gold dust. The carat is 4 grains; that is, diamond grains, which differ slightly from troy grains, as it takes five of the former to weigh four of the latter; or more exactly, one carat = 3.174 gr. troy.

The carat is universally employed in the commerce of jewelry, but it is not rigorously the same in all countries. The following are the weights of the different carats in milligrammes.--

Brazil, 205.750

France, 205.500

England, 205.409

Holland, 205.044

Spain, 205.393

The carat is divided into 1/2, 1/4, 1/8, 1/16, 1/32, 1/64 of the carat. The table of weights of a jeweller's balance should contain from the weight of a thousand carats to these fractions.

The balance employed by dealers in precious stones is a simple little balance which is held in the hand: and yet "such is the experienced quickness of the lapidary," says M. Helphen, "that the balance of the assayer will never find him wrong by even the 64th part of a carat."

Rough crystallized diamonds are valued at from 16 1/2 to 19 dollars the carat, for assorted lots containing no diamonds of more than one carat. Above this weight prices are a different affair.

The rule made known two hundred years ago by Tavernier, that "the prices of two diamonds are proportioned to the squares of their weights," is endorsed by some modern lapidaries. According to this rule, since a one-carat stone of the first water, well cut and without flaws, is valued at about $93, a stone of two carats should be worth four times that, or $372; and one of three carats, nine times as much, or $837.