160 THE DIAMOND MINES OF SOUTH AFRICA
writing,
in the middle of the eighteenth century, there was no uniform standard
of valuation and that the purchase of large stones in particular was
essentially a gambling speculation. In the East Indian market there was
a persistent effort to maintain fixed prices, and there was
comparatively little fluctuation in the market rates of the East Indian
stones, but the diamonds of Brazil were thrown irregularly on the
market, so that the supply ranged from a dearth to a glut, and the
prices were so greatly fluctuating that any investment in these stones
was extra hazardous. Mr. Jeffries marked clearly the disastrous
consequences of greatly varying products and prices in the marketing of
precious stones. He reached the conclusion " that to maintain as
invariable a price of these jewels [diamonds] as is possible must be of
the greatest utility to the public," and gave high praise to the owners
of East Indian diamond fields and diamond merchants because they did
not flood the market regardless of the diamond, like the Brazilian
producers. He notes a shift of fully 23 per cent in the market
rate of diamonds in a single year. In 1733 the value of Brazil diamonds
fell to a point below 20 shillings per carat for rough diamonds, and
within 10 years ran up to more than treble this price.
One
of the simplest and oldest divisions in grading and in the measure of
values of diamonds and other precious stones is in accordance with
their weight. The transmitted measure of weight is the carat, derived
from the Greek κβράτι,ον, the fruit of a variety of acacia,
whose remarkably uniform seeds served as convenient measures of value
of diamonds and other precious stones, and is equivalent to 4 grains
avoirdupois or 3.174 grains troy weight. In market quotations from year
to year and in contracts for sorted diamonds the valuation is expressed
in a stated price per carat. Von Tschudi states that the word carat is
derived from kaura, an African creeping plant, whose red seeds specked
with black were used for weighing gold in Africa and diamonds in India.
On the supposition that £2 may be reckoned the general or average price of a rough diamond of one carat weight, Mr. Jeffries gives two methods or formulas
