whether the mine might be a good in-
vestment after all.
“Our view was that there was value
in AK6 that De Beers were definitely
not seeing,” Lamb told me.
Lucara bid on the site, and Lundin
provided a bank guarantee to De Beers
for fifty million dollars, capturing some
seventy per cent of the stake. Soon af-
terward, Lucara bought the remaining
stake by acquiring De Beers’s London-
based junior venture partner, African
Diamonds. Lucara now owned AK6,
having spent a little more than seventy
million dollars—not much more than
the cost of the most expensive diamond
later found at the site, which became
the Karowe mine. Recently, I asked Eira
Thomas whether she knew then that
her company had bought an asset that
would yield extraordinary stones. She
told me, “No, we got lucky. We knew
there was upside. We didn’t know how
much upside.”
Gren Thomas dismissed the idea
that Lucara had been lucky. His daugh-
ter, he said, was both a workaholic and
a rigorous scientist. Although it was
“beyond anyone’s dreams” that the big-
gest diamond since the Cullinan would
be discovered at Karowe, he felt that
Eira had an unteachable talent for dis-
covery. “She has a good smell for things
that are liable to be successful,” Gren
told me. “She has a good nose, as they
say in our business.”T
he Karowe mine is now a giant
hole, about twenty-six hundred
feet in diameter and about five hun-
dred feet deep. Lucara plans to con-
tinue open-pit mining for seven more
years, until a depth of thirteen hundred
feet is reached, at which point it will
make no economic sense to go further
with this method. (To make such as-
sessments, the firm uses “strategic mine-
planning software” with the pleasing
name Whittle.) Recently, Lucara con-
ducted a feasibility study, which sug-
gested that after the open-pit process
is finished it would be economical to
dig an underground shaft that would
descend another thirteen hundred feet.
Karowe will likely produce diamonds
until 2040.
When I visited Karowe, on an oven-
hot day in September, I peered over theprecipice. A dozen giant diggers and
transport trucks at the bottom of the
cavity looked comically small. The gray
ore of the kimberlite pipes was easily
distinguishable from the reddish-brown
earth around it: ink blots on old paper.
On one side of the mine was the “north
lobe” of kimberlite; on the other was
the south lobe. Around eight hundred
people work at Karowe, the vast ma-
jority of them Botswanans. Lucara is
considered a good employer, but it runs
a tight ship. In 2017, noting inefficien-
cies in its production cycle, it fired many
of its managers and replaced its min-
ing contractor.
One of Lucara’s geologists, Thebe
Tlhaodi—who is known as Fresh, on
account of his babylike rolls of fat—
pointed to a small area, in the south
lobe, from which most of the largest
diamonds had emerged.
“That is our G-spot,” Fresh told me.
“Sweet spot!” a colleague cried out,
laughing. “Sweet spot, Fresh.”
The mine wall was a series of cork-
screw ridges, along which transport
trucks ferried diamond-bearing ore to
the top. The ore was then driven half a
mile or so, to Karowe’s diamond-pro-
cessing plant—a system of conveyor
belts, funnels, and chutes that led the
ore to a sorting warehouse, like a steam-
punk amusement-park ride.
The ore at Karowe is low grade,
meaning that there is a small percent-
age of diamonds in every ton of mate-
rial. (Karowe produces about fifteen
carats per hundred tons of ore; Diavik,
the Canadian mine, produces as much
as a thousand carats.) Recovering a di-
amond at Karowe is tantamount to find-
ing a needle in a haystack, in a barn full
of other haystacks without needles.
The diamond-recovery process is
necessarily destructive: an engineer who
works with Lucara described it as “turn-
ing big rocks into little rocks.” The mined
ore is crushed several times before it
reaches the sorting rooms. Diamonds
have a reputation for being tough, but
if you put them under enough pressure
they will break, along fissure lines. Per-
versely, the same process that is required
to find a profitable yield of diamonds
can lead to the most valuable stones—
the big ones—being pulverized.
Early in Karowe’s operation, Lucara’s
geologists realized that the mine con-