The Diamond Certification Laboratory of Australia (DCLA)
Buy and sell diamonds with the help of the experts
Gem Diamonds has recovered a high quality 233 ct Type II white diamond from its 70% owned Letšeng mine, in Lesotho, the highest dollar per carat kimberlite diamond mine in the world.
This follows the recent recovery of a high quality 442 ct Type II diamond, one of the world’s largest gem quality diamonds to be recovered this year.
The company noted in a trading statement published in July that the mine had produced about 43 275 ct of diamonds in the first half of this year.
Source: miningweekly
A small diamond miner that has dug some of the world’s most valuable gems from a mountainous African kingdom has found another huge stone.
Gem Diamonds Ltd. said Friday it had an unearthed a 442-carat diamond at its Letseng mine in Lesotho. While it’s hard to establish a price for such stones before cutters can evaluate them, it could sell for as much as $18 million, Edward Sterck, analyst at BMO Capital Markets, wrote in a note.
Given the rarity of such large stones, demand for big diamonds has traditionally been resilient, even at times when the wider industry has struggled.
The Letseng mine is famous for the size and quality of the diamonds it produces and has the highest average selling price in the world. Two years ago Gem Diamonds found a 910-carat stone, the size of two golf balls, that sold for $40 million.
The find comes as the global diamond industry has been brought to its knees by the pandemic. Jewelry stores have closed and India’s cutting industry, which handles almost all of the world’s stones, has come to a halt. The miners that dominate the industry, De Beers and Russian rival Alrosa PJSC, have seen their rough diamond sales collapse.
“The recovery of this remarkable 442 carat diamond, one of the world’s largest gem quality diamonds to be recovered this year, is further confirmation of the caliber of the Letseng mine and its ability to consistently produce large, high quality diamonds,” Clifford Elphick, Gem’s chief executive officer, said in the statement.
Source: bloomberg
The famous Cullinan diamond, which is now the centrepiece of the British Crown Jewels, likely originated in Earth’s lower mantle, right beneath the rigid and stable continental plates, where the mantle is slowly moving or convecting.
The finding is part of ongoing research carried out by Evan Smith and Wuyi Wang at the Gemological Institute of America. The new insight was presented by Smith at the virtual 2020 Goldschmidt Conference organized by US-based Geochemical Society and the European Association of Geochemistry.
Smith and his team concluded that the Cullinan diamond was likely formed in the lower mantle and can be considered a ‘super-deep’ stone after examining an analog, large 124-carat diamond from Gem Diamonds’ (LON: GEMD) Letšeng mine in Lesotho.
According to the researchers, recent analyses of this walnut-sized diamond revealed that it contains remains of an important element: bridgmanite.
“Finding these remnants of the elusive mineral bridgmanite is significant. It’s very common in the deep Earth, at the extreme pressure conditions of the lower mantle, below a depth of 660 kilometres, even deeper than most super-deep diamonds,” Smith said in his presentation. “Bridgmanite doesn’t exist in the upper mantle, or at the surface. What we actually see in the diamonds when they reach the surface is not bridgmanite, but the minerals left when it breaks down as the pressure decreases. Finding these minerals trapped in a diamond means that the diamond itself must have crystallized at a depth where bridgmanite exists, very deep within the Earth.”
By aiming a laser at the tiny inclusions trapped inside the diamond, the researchers found that the way the light scattered (using a Raman spectrometer) was characteristic of bridgmanite breakdown products.
The Letšeng mine diamond is so pure that it doesn’t contain nitrogen in its crystal structure. This characteristic classifies it as a ‘Clippir’ diamond, which is the same category as that of the Cullinan diamond.
“What is special about this one is that it is the first Clippir diamond for which we can firmly assign a lower mantle origin, that is, below 660 kilometres,” Smith said. “Previously, we had known that Clippir diamonds are super-deep and speculated that their depth of origin might span 360 to 750 kilometres depth, but we hadn’t actually seen any that were definitely from the deeper end of this window.”
In the researcher’s view, this finding gives a better idea of exactly where Clippir diamonds come from and also shows that there is some overlap in the birthplace for Clippir diamonds and type IIb diamonds, such as the famous Hope diamond. This rare blue gem was owned by monarchs, bankers, heiresses and thieves until it landed at the Smithsonian National Museum of Natural History in Washington DC.
The overlap that Smith refers to points to a previous study in which the researcher showed that the Hope and other IIb diamonds originate in Earth’s deep mantle and that the boron that gives them a blue hue comes from the bottom of the oceans. To get into the diamond, the element is first dragged hundreds of kilometres by plate tectonics down into the mantle.
“It shows that there is a gigantic recycling route that brings elements from Earth’s surface down into the Earth, and then occasionally returns beautiful diamonds to the surface, as passengers in volcanic eruptions,” Smith said.
Souce: mining.com
Gem Diamonds has recovered a number of large, high-quality stones at its Letšeng mine in Lesotho, all found in the first week after production resumed following the COVID-19 lockdown.
They include a 60-carat, light-yellow, type I diamond, and three D-color, white, type II diamonds weighing 87, 66 and 23 carats, the company said Monday. It also found several diamonds over 10.8 carats.
Between February and March, the miner unearthed four white diamonds weighing 88, 56, 53 and 33 carats. It has also retrieved two diamonds over 100 carats so far this year, and a 13.33-carat pink.
Gem Diamonds restarted production at Letšeng last week after the government allowed the mining sector to reopen following an extended shutdown. Lesotho remains on lockdown until May 5.
Source: Diamonds.net
Gem Diamonds has recovered a 135 carat yellow at its Letšeng mine in Lesotho, the third significant colored-diamond discovery at the deposit this year.
The company retrieved the high quality, type I stone on June 21, three months after the mine yielded a similar quality yellow diamond weighing 134 carats. Those discoveries follow a two year gap in the recovery of yellow diamonds weighing more than 100 carats from Letšeng. In June 2017, the miner found a 151.52 carat yellow.