THENEWYORKER,FEBRUARY3, 2020 39
tained exceptional stones. Many of the
diamonds were large, and most of them
were Type IIa—“ultra-deep” stones that
originated more than three billion years
ago, sometimes at six hundred kilome-
tres or more beneath the surface. These
diamonds, which are often beautiful
and clear, with irregular shapes, present
challenges to discovery. Among other
things, they do not fluoresce, because
they are low in nitrogen. Many tradi-
tional plants use X-ray luminescence
to sort diamonds in the final stages of
processing. That approach would not
work well at Karowe.
L
ucara decided to innovate. Karowe
was built with an autogenous mill—
rocks were placed in a rotating drum,
where they cascaded into one another.
This was a less violent method of break-
ing stones than the technique commonly
used in southern Africa, in which steel
rods smash rocks into smaller pieces.
By 2013, Eira Thomas had persuaded a
Canadian geologist named John Arm-
strong, who had worked with her at
Stornoway, to join Lucara. Armstrong
has a nimble intelligence. When he
came to the firm, it had already recov-
ered a few large diamonds. Statistical
models convinced him that Karowe had
many more such stones—and his team
began to explore ways to recover them
without damaging them. One option
that Armstrong considered was X-ray
transmission technology, known as XRT,
which scans objects for a specific atomic
signature, rather than for a physical
characteristic, such as luminescence or
weight. The engineer who works with
Lucara told me that an XRT machine
functions much “like an airport bag-
gage scanner.”
XRT had flourished in the recycling
industry, and some mines used it as a
secondary recovery method, but it had
never been used as a principal method.
Lucara’s management quickly saw its
potential. If the technology worked well
enough, the mine’s larger diamonds
would not be crushed so many times
before they were sorted. The scanner
could pick out anything with a carbon
signature. At the end of a conveyor belt,
a puff of air would propel a rough dia-
mond into a separate chute, where it
would travel down to a sorting room.
In 2014, Lucara signed a deal with
a firm called TOMRA, a leader in gar-
bage-recycling technologies but a small
player in the mining field. The arrange-
ment required an investment of between
fifty and sixty million dollars by Lu-
cara. Not only would Lucara need to
buy half a dozen XRT machines from
TOMRA; it would also have to reconfigure
its whole diamond-processing plant
around them. The financial risk was
significant. Geoffrey Madderson, the
diamond-segment manager at TOMRA,
signed the deal, and he told me that,
for Lucara, “the whole future of its busi-
ness was at stake.”
While six conventional XRT ma-
chines were being installed at Karowe,
a pilot machine was put in place. This
device, Lucara hoped, would recover
diamonds weighing three hundred carats
or more—rare items, even at Karowe.
In the device’s first few months of op-
eration, it did not isolate a single dia-
mond, and tensions among Lucara’s
management team rose. “It was a roar-
ing success, apart from the fact that
we didn’t recover any diamonds,” Mad-
derson recalled. “People said that it
was a farce.”
But Madderson and Armstrong
noted that the pilot XRT had been pro-
cessing only ore from the north lobe,
which was not rich in large diamonds.
Lucara kept faith with the technology,
and in April, 2015, the whole plant
switched over to the XRTs. On the first
weekend of using the new system, the
scanners found a two-hundred-and-sixty-
nine-carat stone. It later sold for about
twenty million dollars. More exceptional
stones followed. Within six weeks, the
investment in the scanners had been re-
paid. Then, in November, 2015, the XRT
machines puffed their air jets onto the
Lesedi La Rona. A day later, Lucara
found an ice-white, eight-hundred-and-
thirteen-carat diamond, now known as
the Constellation. In the next few days,
a string of other “specials” unspooled
along the conveyor belts of Karowe’s
sorting rooms. In aggregate, these rough
diamonds fetched more than a hundred
million dollars in sales.
Eira Thomas was ecstatic: the firm’s
creative approach had been validated.
By her reckoning, De Beers would not
have recovered such large stones from
Karowe, even if it had developed the
mine. The consortium’s processes were
too crude. (De Beers declined to com-
ment for this article.) Thomas told me,
“One of the things that I love about
our team—and this stems from the ex-
perience of Diavik—is that, as Cana-
dians, we didn’t have a big history of ex-
ploring for diamonds. And that was the
biggest advantage that we had.”
Madderson told me that, for the di-
amond industry, Lucara’s discovery of
the Lesedi La Rona was momentous—
an instant in which a new technology
changes a business forever, leaving be-
hind those who fail to adapt. He was
on a work trip in Russia when he heard
the news. “That day was a fucking good
day,” he said.
A
large rough diamond presents both
an opportunity and a risk. Two
years after the Cullinan was discovered
in South Africa, it remained unsold.
Eventually, in 1907, the government of
Transvaal, in South Africa, decided to
buy the stone, for about twenty million
dollars in today’s money, and present it
as a gift to Edward VII. The King se-
lected two Dutch brothers, Joseph and
Abraham Asscher, the most renowned
diamond cutters of their day, to turn
the stone into jewels. A Royal Navy
ship was publicly instructed to trans-
port the Cullinan to the brothers’ stu-
dio, in Amsterdam. In fact, the ship was
guarding an empty box, as a decoy. Abra-
ham Asscher collected the stone from
the Colonial Office, in London, and
then travelled back to Amsterdam, by
ferry and by train, with the diamond in
his pocket. (Security arrangements for
large diamonds have remained rudi-
mentary: in the nineteen-fifties, the
New York jeweller Harry Winston re-
ceived big stones by registered first-class
mail; the Lesedi La Rona was carried
“on the person” of unguarded commer-
cial-airline passengers.)
Joseph Asscher, the more skillful
brother, was given the task of cleaving
