Saturday, 19 May 2018

WE HAVE RECOVERED LARGE GEMS : ZCDC

There is fresh hope for local diamond mining after the Zimbabwe Consolidated Diamond Company (ZCDC) started extracting ‘tennis ball-like diamonds,’ including a 23 carat gem quality and a 65 carat near-gem from its flagship operations in Chiadzwa.

This has seen ZCDC setting the stage for the commissioning of a 450 tonnes of ore per hour conglomerate plant to recover large diamonds.

At the moment, a mega diamond recovery (MDR) circuit has been incorporated to recover large stones from the jaw crusher product before it reports to the secondary cone crushers for further size reductions, in a move that prevents breakage of any existing large stones.

ZCDC chief executive officer, Dr Morris Mpofu told The Sunday Mail Business on the sidelines of the Chamber of Mines of Zimbabwe congress in Victoria Falls last week that they were excited about the latest developments.

“We are pleased to announce the recovery of some large diamonds from our flagship operations in the Chiadzwa area,” said Dr Mpofu.

“The latest and largest recoveries include a 23 carat gem quality stone, a 65 carat near-gem quality stone and a 45 carat borat stone.
“The recovery of these large stones underline the large stone potential of the Chiadzwa diamond fields.”

Zimbabwe joins other diamond mining countries such as Botswana, Angola, Russia, Tanzania, Lesotho and Sierra Leone, in extracting large diamonds.
The recovery of large diamonds has been rising in the last two years, with the London Stock Exchange listed Gem Diamonds recovering an exceptional gem quality 149 carat from its Letseng Mine in Lesotho on January 15 this year.

The 149 carat diamond was the fourth top quality stone of over 100 carats recovered to date in 2018, from the Letseng Mine.

Letseng Mine has also hauled a 910 carat gem this year. Botswana has also recovered a 472 carat diamond and a 327 carat, both at Karowe Diamond Mine which is operated by Lucara Diamond Corp.

In November 2015, Lucara also recovered the 1,111-carat “Lesedi La Rona”.
At that point, Lucara’s market capitalisation was slightly over US$500 million while the estimated value of the diamond was US$75 million, representing 15 percent of the firm’s total value.

Dr Mpofu said ZCDC is now seeking to understand better the emplacement, occurrence, characteristics and distribution of the large diamonds, through geological drilling and sampling.

ZCDC’s chief geologist Mr Owen Chihota is undertaking the drilling and sampling.
Indications are that the sediments in Chiadzwa diamond fields were deposited in a large basin over a period of time under different environmental and climatic conditions prevailing then.

Dr Mpofu said the basal conglomerate, which hosts diamonds and the overlying sandstones and grits, show a period of high energy activity whereby the river systems brought in a lot of eroded materials into the basin that were later deposited at the base.

The chief geologist has indicated that the large conglomerate clasts of more than 10cm in size have been observed in the basal conglomerate in Chiadzwa basin.

Said Dr Mpofu: “Where there are troughs within the basement profile, the conglomerate is typically of large clast sizes. As a basic rule, the larger the clasts the larger the diamonds.

“ZCDC expects to find large diamonds within the basin; larger diamonds would settle in similar depositional environments as the larger mature clasts.”
The national diamond miner has already sent samples of conglomerate ore to a laboratory in South Africa for analysis so as to determine the origin of the indicator minerals and the potential distance travelled in order to establish the primary kimberlite source.


Currently, ZCDC’s operations have installed technology that is limited to the recovery of stones up to 30mm. Sunday Mail

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