Marco Polo's account of how diamonds are obtained is ingenuous
in its reckless defiance of fact. He says that in the mountains
"there are certain great deep valleys to the bottom of which there
is no access. Wherefore the men who go in search of the diamonds
take with them pieces of meat," which they throw into this deep
valley. He relates that the eagles, when they see these pieces of
meat, fly down and get them, and when they return, they settle on
the higher rocks, when the men raise a shout, and drive them off.
After the eagles have thus been driven away, "the men recover the
pieces of meat, and find them full of diamonds, which have stuck to
them. For the abundance of diamonds down in the depths," continues
Marco Polo, naively "is astonishing; but nobody can get down, and
if one could, it would be only to be incontinently devoured
by the serpents which are so rife there." A further account proceeds
thus: "The diamonds are so scattered and dispersed in the earth,
and lie so thin, that in the most plentiful mines it is rare to
find one in digging;... they are frequently enclosed in clods,...
some... have the earth so fixed about them that till they grind
them on a rough stone with sand, they cannot move it sufficiently
to discover they are transparent or... to know them from other
stones. At the first opening of the mine, the unskilful labourers
sometimes, to try what they have found, lay them on a great stone,
and, striking them one with another, to their costly experience,
discover that they have broken a diamond.... They fill a cistern
with water, soaking therein as much of the earth they dig out of
the mine as it can hold at one time, breaking the clods, picking
out the great stones, and stirring it with shovels... then they
open a vent, letting out the foul water, and supply it with clean,
till the earthy substance be all washed away, and only the gravelly
one remains at the bottom." A process of sifting and drying is then
described, and the gravel is all spread out to be examined, "they
never examine the stuff they have washed but between the hours of
ten and three, lest any cloud, by interposing, intercept the brisk
beams of the sun, which they hold very necessary to assist them
in their search, the diamonds constantly reflecting them when they
shine on them, rendering themselves thereby the more conspicuous."

The earliest diamond-cutter is frequently mentioned as Louis de
Berquem de Bruges, in 1476. But L