The second-largest diamond in history was probably twice as big
before it broke into pieces, researchers at the Gemological Institute of
America (GIA) have claimed.
Similarities between the 1,109-carat Lesedi La Rona, the 812-carat
Constellation and three other stones suggest they were all one large
piece of rough weighing at least 2,774 carats before volcanic eruptions
or mining processes split them up, the GIA said this week.
Lucara Diamond Corp., which discovered all five diamonds at its
Karowe mine in Botswana in November 2015, had already claimed that one
of them, a 374-carat stone, was once attached to the Lesedi La Rona. The
GIA last year studied three of the other stones — the Constellation, as
well as diamonds weighing 296 carats and 183 carats — and speculated
that they were also from the same rough.
The theory was strengthened after the GIA gained access to faceted
diamonds from the Lesedi La Rona and the 374-carat stone earlier this
year, Dr. Ulrika D’Haenens-Johansson, a senior research scientist at the
GIA, told
Rapaport News Wednesday.
The five diamonds had similar visual characteristics in their rough
form, and came from the same part of the Karowe mine at the same time.
They also gave results under close gemological analysis that were so
similar that it’s unlikely they were unrelated, Dr. D’Haenens-Johansson
said. The nature of some of the stones’ surfaces also suggested they had
become detached from each other.
“After the 2017 study, all we could do was speculate that all five
stones were from the same rough,” she added. “After having the
opportunity to examine all five stones in 2018, we are able to reach
stronger conclusions. It is probable that there are other unaccounted
pieces that would have been part of this historic rough.”
Lucara CEO Eira Thomas said the company had no reason to disagree
with the GIA’s findings. Evidence indicates the larger stone broke up
both because of natural effects and being knocked around during the
recovery process, Thomas noted.
The company used X-ray transmission (XRT) technology to help it
recover the five large diamonds. It has since installed additional XRT
equipment at Karowe to ensure it unearths exceptional stones as early as
possible in the process.
D’Haenens-Johansson presented the findings at the GIA’s International
Gemological Symposium in Carlsbad, California, in October, and
published a summary in the Fall 2018 issue of
Gems & Gemology,
the institute’s quarterly journal.
The institute is preparing a full,
peer-reviewed article in a forthcoming edition of the publication.
Lucara sold the 374-carat diamond to Graff for $17.5 million in May
2017, and subsequently sold the Lesedi La Rona to the same company for
$53 million in September of that year. Graff recently unveiled several
polished diamonds it had cut from the 1,109-carat rough.
The Constellation went for $63.1 million in 2016 to a partnership
comprising Dubai-based Nemesis International and Swiss jeweler De
Grisogono.
Image: The Lesedi La Rona. (Donald Bowers/Getty Images/Sotheby’s).
Source:
DCLA