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Jeffries Treatise on Diamonds and Pearls

Book Name: Treatise on Diamonds and Pearls

Author: Jeffries

Published: 1753

As the following treatise is calculated to inform the world concerning the value of diamonds and pearls; the weights made use of relative thereto are here previously ex­plained, as the knowledge of them will be found necessary to the public. They agree the nearest to troy weight of any other, and are commonly called carat weights; 150 carats make about an ounce of that weight. Carats are divided into halves, quarters, or grains; eighths, sixteenths, and thirty-two parts.

The draughts of the sizes of brilliant and rose diamonds, exhibited in the plates, are tests to prove the truth and defects of the manufacture of any diamond, and will be found as necessary as scales and weights, in attaining to a right judgment of their value. To make the truth of this assertion appear more evident, it is here to be observed ; first, that either a brilliant or rose diamond may be wrought in such a manner as to con tain one fourth, or even one third, more weight than it ought to have, which neces­sarily injures the beauty of its form, and likewise injures its true spirit and lustre ; and, if that overweight be injudiciously va­lued, together with its due weight, the price will be thereby greatly heightened above its just value, more especially in large diamonds.

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Jeffries Treatise on Diamonds and Pearls