74 THE VALUE OF DIAMONDS book ii
It
is first necessary to ascertain the weight of the diamond, and next to
see if it is perfect, whether it is a thick stone, square-shaped, and
having all its angles perfect; whether it is of a beautiful white
water, and bright, without points, and without flaws. If it is a stone
cut into facettes, which is ordinarily called ' a rose', it is
necessary to observe whether the form is truly round or oval; whether
the stone is well-spread, and whether it is not a lumpy stone ; and,
moreover, whether it is of uniform water, and is without points and
flaws, as I described the thick stone.
A stone of this quality, weighing 1 carat, is worth 150 livres 1 or
more, and supposing it is required to know the value of a stone of 12
carats of the same degree of perfection, this is how it is to be
ascertained : Square the 12, this amounts to 144 ; next multiply 144 by
150, i. e. the price of 1 carat, and it amounts to 21,600 livres—12 x
12 x 150 = 21,600.a This is the price of a diamond of 12 carats.
But
it is not enough to know the price of only perfect diamonds, one must
know also the price of those which are not so ; this is ascertained by
the same rule, and on the basis of the price of a stone of 1 carat.
This is an example : Suppose a diamond of 15 carats which is not
perfect, the water being not good, or the stone badly shaped, or full
of spots or flaws. A diamond of the same nature, of the weight
1 Say £11 5s., at Is. 6d. to
the livre. Thevenot gives 15 to 16 ecus as the price of stones of 1 or
2 mangelins, but those of 3 mangelins were worth at the rate of 30 ecus
the mangelin. (Voyages des Indes, Paris, ed. 1684, p. 289.) As
Thevenot gives the value of a mangelin at 1-6 carats, 3 would be equal
to 4.8 carats, and the price of 90 ecus, or £20 5s., while Tavernier's valuation for a stone of 4.8 carats would be 4.8X 4.8x 150 = 3,456 livres = £259 is. This enormous discrepancy must be due to a mistake by Thevenot.
2
i. e. £1,620. Whatever may have been the case, it is now apparent that
no hard and fast rule can be given to determine the selling value of
diamonds, as it is subject to very great variations. Among other
formulae, however, the following may be mentioned :
— (m X 2) o where m = the number of carats, and a the value of 1.
This is given in Handbuch der Edelstein, A. Schrauf, Vienna. A stone of 12 carats, similar in quality to that above given, so calculated, would be worth £945.
