Tuesday, 11 December 2018

Coarse concentrator makes space for larger diamonds



Jwaneng has installed fit-for-purpose coarse concentrators from DebTech that will provide the mine the capability to recover large diamonds.

The two x-ray transmission (XRT) coarse concentrator plus (CC+) units were designed and manufactured by De Beers Technologies (DebTech) at its facilities near Johannesburg, and will be commissioned at Jwaneng by the end of 2018.

Located 120 km from Botswana’s capital Gaborone, Jwaneng is owned by Debswana – a joint venture between the Republic of Botswana and De Beers Plc; it is one of the world’s most valuable diamond mines by reserve value.

“The XRT CC+ units at Jwaneng are upscaled versions of our XRT coarse concentrator model,” says Gordon Taylor, head of DebTech.

“When initially considering Jwaneng’s requirements, we felt confident, given our history of developing these types of machines, that we could engineer the best solution for them.”

The two CC+ ore sorters form the heart of a new large diamond recovery pilot plant at Jwaneng.

Design and construction of the XRT CC+ units began in January 2017 and they were delivered to Debswana in January 2018 for early integration into the plant.

What makes this application different from the typical application of the ore sorting units, says Taylor, is the position of the units right at the front end of the plant.

Generally, they are located further down the process, where throughput requirements are not as onerous.
“This installation, on the other hand, will be treating coarse sized run-of-mine (ROM) material, so must handle substantial throughput quantities of up to 500 tph,” he says.

While it has long been considered quite likely that the Jwaneng pipe could contain large diamonds, previous processing techniques did not lend themselves to a simple elegant recovery system.

“The recent development of more cost-effective processing techniques based on improved XRT technology has changed the economics of finding larger diamonds,” he says.

The XRT technology is also valuable for replacing coarse and middles dense media separation (DMS), says Taylor, as the typical XRT concentrate yield is significantly less than an equivalent DMS plant.

“This considerably reduces downstream infrastructure.”

“XRT consumes much less power and water, does not require a consumable material such as ferrosilicon and is much more accurate at identifying and sorting diamonds,” indicates Taylor.

In the XRT sorting unit, material enters the unit via the inlet chute and is transported by the feeder to an internal conveyor belt, where it passes between the X-ray source and the X-ray camera.

The camera images are analysed by software algorithms and – if a diamond is identified – then a pneumatic ejection system is activated to divert the stone to a concentrate chute.

“The system provides continuous x-ray transmission images of material being processed, and these images are used to accurately discriminate between material types,” he says.

“The ‘Dual Energy’ feature on XRT sorting systems is a further enhancement that improves the technique’s ability to analyse materials of differing thickness.”

The powerful imaging capabilities of the system allows not only identification and ejection of diamonds – be they low-luminescent, type II, coloured or boart – but the generation of online carat estimates and stone count values.
He also highlights the accuracy of the latest XRT technology in the CC+ units in efficiently treating large volumes of material.

“The latest XRT technology minimises the number of ‘false positives’ that the system identifies, and therefore cuts down drastically on the amount of mined material that must be unnecessarily accommodated in downstream processing capacity,” he says.

“This accuracy transforms the economics of the whole process, and makes for much more efficient minerals processing.”

Supplied in 12 m shipping containers, the CC+ units are designed to conveniently include all the related technology and services that the customer will need to operate the plant.

The containerised solution generally requires only an electrical power source and a water connection.

Each sorter is self-contained with its own dedicated control room, internal water and electrical power conditioning, and internal compressed air generation.

Ease of use is ensured by a user-friendly, menu-driven control interface for the operator and the machines are fully integrated into the plant control system.

“The containerised configuration means that we can construct and test the machines under controlled workshop conditions, ensuring that all aspects are ready for commissioning by the time the unit leaves our facilities,” says Taylor.

“Containerisation also makes it simpler to transport the units to site and to off-load, while reducing commissioning time considerably.”

DebTech will also be supplying full maintenance support for the CC+ units, which are fitted to provide remote diagnostics.

“In summary, the XRT CC+ sorters supplied to Jwaneng will optimise diamond recovery with minimum gangue material at high feed-rates, while providing the customer with the highest chances of recovering large stones,” says Taylor.

Coarse concentrator makes space for larger diamonds



Jwaneng has installed fit-for-purpose coarse concentrators from DebTech that will provide the mine the capability to recover large diamonds.

The two x-ray transmission (XRT) coarse concentrator plus (CC+) units were designed and manufactured by De Beers Technologies (DebTech) at its facilities near Johannesburg, and will be commissioned at Jwaneng by the end of 2018.

Located 120 km from Botswana’s capital Gaborone, Jwaneng is owned by Debswana – a joint venture between the Republic of Botswana and De Beers Plc; it is one of the world’s most valuable diamond mines by reserve value.

“The XRT CC+ units at Jwaneng are upscaled versions of our XRT coarse concentrator model,” says Gordon Taylor, head of DebTech.

“When initially considering Jwaneng’s requirements, we felt confident, given our history of developing these types of machines, that we could engineer the best solution for them.”

The two CC+ ore sorters form the heart of a new large diamond recovery pilot plant at Jwaneng.

Design and construction of the XRT CC+ units began in January 2017 and they were delivered to Debswana in January 2018 for early integration into the plant.

What makes this application different from the typical application of the ore sorting units, says Taylor, is the position of the units right at the front end of the plant.

Generally, they are located further down the process, where throughput requirements are not as onerous.
“This installation, on the other hand, will be treating coarse sized run-of-mine (ROM) material, so must handle substantial throughput quantities of up to 500 tph,” he says.

While it has long been considered quite likely that the Jwaneng pipe could contain large diamonds, previous processing techniques did not lend themselves to a simple elegant recovery system.

“The recent development of more cost-effective processing techniques based on improved XRT technology has changed the economics of finding larger diamonds,” he says.

The XRT technology is also valuable for replacing coarse and middles dense media separation (DMS), says Taylor, as the typical XRT concentrate yield is significantly less than an equivalent DMS plant.

“This considerably reduces downstream infrastructure.”

“XRT consumes much less power and water, does not require a consumable material such as ferrosilicon and is much more accurate at identifying and sorting diamonds,” indicates Taylor.

In the XRT sorting unit, material enters the unit via the inlet chute and is transported by the feeder to an internal conveyor belt, where it passes between the X-ray source and the X-ray camera.

The camera images are analysed by software algorithms and – if a diamond is identified – then a pneumatic ejection system is activated to divert the stone to a concentrate chute.

“The system provides continuous x-ray transmission images of material being processed, and these images are used to accurately discriminate between material types,” he says.

“The ‘Dual Energy’ feature on XRT sorting systems is a further enhancement that improves the technique’s ability to analyse materials of differing thickness.”

The powerful imaging capabilities of the system allows not only identification and ejection of diamonds – be they low-luminescent, type II, coloured or boart – but the generation of online carat estimates and stone count values.
He also highlights the accuracy of the latest XRT technology in the CC+ units in efficiently treating large volumes of material.

“The latest XRT technology minimises the number of ‘false positives’ that the system identifies, and therefore cuts down drastically on the amount of mined material that must be unnecessarily accommodated in downstream processing capacity,” he says.

“This accuracy transforms the economics of the whole process, and makes for much more efficient minerals processing.”

Supplied in 12 m shipping containers, the CC+ units are designed to conveniently include all the related technology and services that the customer will need to operate the plant.

The containerised solution generally requires only an electrical power source and a water connection.

Each sorter is self-contained with its own dedicated control room, internal water and electrical power conditioning, and internal compressed air generation.

Ease of use is ensured by a user-friendly, menu-driven control interface for the operator and the machines are fully integrated into the plant control system.

“The containerised configuration means that we can construct and test the machines under controlled workshop conditions, ensuring that all aspects are ready for commissioning by the time the unit leaves our facilities,” says Taylor.

“Containerisation also makes it simpler to transport the units to site and to off-load, while reducing commissioning time considerably.”

DebTech will also be supplying full maintenance support for the CC+ units, which are fitted to provide remote diagnostics.

“In summary, the XRT CC+ sorters supplied to Jwaneng will optimise diamond recovery with minimum gangue material at high feed-rates, while providing the customer with the highest chances of recovering large stones,” says Taylor.

Monday, 10 December 2018

LUCAPA TO SELL LARGE AND EXCEPTIONAL DIAMONDS IN “HISTORIC” AUCTION



Lucapa Diamond Company, owner and operator of the Lulo mine in Angola, will sell seven large and exceptional Lulo diamonds an “historic inaugural international tender under Angola’s new diamond marketing laws” in January.

The auction, which will be held at the offices of Sodiam Angolan state diamond marketing company in Luanda, will feature “major international diamantaires and large stone manufacturers”. The seven Lulo diamonds to be offered at tender include Type IIa D colour white gems of up to 114 carats and a 46 carat pink diamond.

In its latest diamond sale, held in late November, Lucapa raked in $4.2 million from the sale of 3,411 carats. The sale achieved an average price per carat of $1,220. The sale has brought the total year-to-date sales of Lulo diamonds to $24.5 million at an average price of $1,353 per carat.

Source: DCLA

LUCAPA TO SELL LARGE AND EXCEPTIONAL DIAMONDS IN “HISTORIC” AUCTION



Lucapa Diamond Company, owner and operator of the Lulo mine in Angola, will sell seven large and exceptional Lulo diamonds an “historic inaugural international tender under Angola’s new diamond marketing laws” in January.

The auction, which will be held at the offices of Sodiam Angolan state diamond marketing company in Luanda, will feature “major international diamantaires and large stone manufacturers”. The seven Lulo diamonds to be offered at tender include Type IIa D colour white gems of up to 114 carats and a 46 carat pink diamond.

In its latest diamond sale, held in late November, Lucapa raked in $4.2 million from the sale of 3,411 carats. The sale achieved an average price per carat of $1,220. The sale has brought the total year-to-date sales of Lulo diamonds to $24.5 million at an average price of $1,353 per carat.

Source: DCLA

Tuesday, 4 December 2018

18ct. Diamond Smashes Estimate at Bonhams



An 18.04 carat diamond fetched $828,500 at Bonhams on Monday, exceeding its presale estimate of $400,000 to $600,000, Bonhams said Tuesday.

The emerald cut, G color, VS2 clarity ring flanked by trillion cut diamonds led the company’s New York Fine Jewelry sale. It was the first time the stone which was from a private collection had appeared at auction.

“We saw some fierce bidding for this magnificent diamond and are delighted with how well it performed,” said Caroline Morrissey, head of sales for Bonhams Jewelr, US.

At the same sale, a solitaire ring by Royal de Versailles featuring a round brilliant cut, 7.01 carat diamond garnered $275,000, beating its estimate of $180,000 to $250,000.

Other notable items from the auction included a pear-shaped brilliant cut, 5.03 carat, D color, internally flawless diamond solitaire ring. The piece went for $250,000, within its original valuation of $200,000 to $300,000.

 A cushion shaped modified brilliant cut, 18.76 carat, fancy light yellow diamond ring flanked by white, trillion shaped diamonds fetched $231,250, smashing its estimate of $100,000 to $150,000.

A rectangular shaped emerald cut, 33.03 carat, deep intense blue Sri Lankan sapphire ring failed to find a buyer, Bonhams said. That piece carried a presale estimate of $250,000 to $350,000.

The auction brought in a total of $4 million, according to Rapaport calculations, which Bonhams declined to confirm.

The auction house will hold its Fine Jewelry sale in London on Wednesday, featuring a 24.31 carat diamond estimated at $1.7 million to $2.3 million.

Source: DCLA

18ct. Diamond Smashes Estimate at Bonhams



An 18.04 carat diamond fetched $828,500 at Bonhams on Monday, exceeding its presale estimate of $400,000 to $600,000, Bonhams said Tuesday.

The emerald cut, G color, VS2 clarity ring flanked by trillion cut diamonds led the company’s New York Fine Jewelry sale. It was the first time the stone which was from a private collection had appeared at auction.

“We saw some fierce bidding for this magnificent diamond and are delighted with how well it performed,” said Caroline Morrissey, head of sales for Bonhams Jewelr, US.

At the same sale, a solitaire ring by Royal de Versailles featuring a round brilliant cut, 7.01 carat diamond garnered $275,000, beating its estimate of $180,000 to $250,000.

Other notable items from the auction included a pear-shaped brilliant cut, 5.03 carat, D color, internally flawless diamond solitaire ring. The piece went for $250,000, within its original valuation of $200,000 to $300,000.

 A cushion shaped modified brilliant cut, 18.76 carat, fancy light yellow diamond ring flanked by white, trillion shaped diamonds fetched $231,250, smashing its estimate of $100,000 to $150,000.

A rectangular shaped emerald cut, 33.03 carat, deep intense blue Sri Lankan sapphire ring failed to find a buyer, Bonhams said. That piece carried a presale estimate of $250,000 to $350,000.

The auction brought in a total of $4 million, according to Rapaport calculations, which Bonhams declined to confirm.

The auction house will hold its Fine Jewelry sale in London on Wednesday, featuring a 24.31 carat diamond estimated at $1.7 million to $2.3 million.

Source: DCLA

Wednesday, 28 November 2018

Sapphire Necklace Sells for $15M at Christie’s



A rare sapphire necklace was the top seller at Christie’s Magnificent Jewels auction in Hong Kong, which garnered about $60 million in total on Tuesday.

The Peacock Necklace, which had a presale estimate of $12 million to $15 million, became the most expensive Kashmir sapphire necklace per carat in auction history, Christie’s said.

 The piece contains 21 cushion-cut Kashmir sapphires weighing a total of 109.08 carats. It fetched $15 million at the sale, achieving a price of $137,146 per carat.

Christie’s also garnered $1.3 million from the sale of the 24.04-carat, fancy-yellow Moon of Baroda pendant, which Marilyn Monroe wore to the premiere of her 1953 movie, Gentlemen Prefer Blondes. The piece smashed its estimate of $500,000 to $750,000. An autographed photo of the actress wearing the necklace fetched $35,302, compared with its original estimate of $10,000 to $15,000.

An oval-shaped, 10.04-carat, Burmese pigeon’s blood ruby and diamond ring brought in $7.2 million in line with an expected $6.9 million to $8.7 million. A set of pear brilliant-cut, fancy-pink earrings weighing 5.21 carats and 5.01 carats sold for $4.3 million, within its presale valuation range of $3.8 million to $4.5 million .

Christie’s sold 70% of lots on offer at the auction.

Image: The Peacock Necklace. (Christie’s)

Source: DCLA

Tiffany Buys Back Titanic Watch for Record $1.97m

Tiffany & Co paid a record $1.97m for a gold pocket watch it made in 1912, and which was gifted to the captain of a ship that rescued mo...