New method could simplify detection of diamond deposits

Geologists from ETH Zurich and the University of Melbourne have established a link between diamond occurrence and the mineral olivine.

In a paper published in the journal Nature Communications, the scientists explain that their method will simplify the detection of diamond deposits. The process relies on the chemical composition of kimberlites, which occur only on very old continental blocks that have remained geologically unchanged for billions of years, predominantly in Canada, South America, central and southern Africa, Australia and Siberia.

According to the study’s lead author, Andrea Giuliani, olivine is a mineral that makes up around half of kimberlite rock and consists of varying proportions of magnesium and iron. The more iron olivine contains, the less magnesium it has and vice versa.

“In rock samples where the olivine was very rich in iron, there were no diamonds or only very few,” Giuliani, who has been studying the formation and occurrence of the gemstones since 2015, said in a media statement. “We started to collect more samples and data, and we always got the same result.”

His investigations ultimately confirmed that olivine’s iron-to-magnesium ratio is directly related to the diamond content of the kimberlite. Giuliani and his team took these findings back to De Beers, who had provided them with the kimberlite samples. The company was interested and provided the scientific study with financial support and asked the researchers not to publish the results for the time being.

A slow, repetitive process
In 2019, Giuliani moved from Melbourne to ETH Zurich and, supported by the Swiss National Science Foundation, began to look for explanations for the connection between olivine’s magnesium and iron content and the presence of diamonds.

With his new colleagues, he examined how the process of metasomatism, which takes place in the earth’s interior, affects diamonds. In metasomatism, hot liquids and melts attack the rock. The minerals present in the rock react with the substances dissolved in the fluids to form other minerals.

The geologists analyzed kimberlite samples that contained olivines with a high iron content—and hence no diamonds. They discovered that olivine becomes richer in iron in the places where melt penetrates the lithospheric mantle and changes the composition of mantle rocks significantly. And it is precisely in this layer, at a depth of around 150 kilometres, that diamonds are present.

The infiltration of the melt that makes olivine richer in iron destroys diamonds. If, on the other hand, no or only a small amount of melt from underlying layers penetrates the lithospheric mantle and thus no metasomatism takes place, the olivine contains more magnesium—and the diamonds are preserved.

“Our study shows that diamonds remain intact only when kimberlites entrain mantle fragments on their way up that haven’t extensively interacted with previous melt,” Giuliani said.

A key point is that kimberlites don’t normally reach the earth’s surface in one go. Rather, they begin to rise as a liquid mass, pick up fragments of the mantle on the way, cool down and then get stuck. In the next wave, more melt swells up from the depths, entrains components of the cooled mantle, rises higher, cools, and gets stuck. This process can happen multiple times.

“It’s a real stop-and-go process of melting, ascent and solidification. And that has a destructive effect on diamonds,” Giuliani noted. If, on the other hand, conditions prevail that allow kimberlites to rise directly to the surface, then this is ideal for the preservation of the gemstones.

De Beers is already using olivine analysis
Olivine analysis is as reliable as previous prospecting methods, which are mainly based on the minerals clinopyroxene and garnet. However, the new method is easier and faster: it takes only a few analyses to get an idea of whether a given kimberlite field has diamonds or not.

“The great thing about this new method is not only that it’s simpler, but also that it finally allows us to understand why the previous methods worked,” Giuliani said. “De Beers is already using this new method.”

Source: DCLA

Botswana Assigns $65M for Stake in Belgian Manufacturer

Botswana has designated BWP 890 million ($65 million) from its new fiscal 2024-2025 budget for the purchase of a 24% stake in Belgian manufacturer HB Antwerp.

The deal, which it first announced in March, calls for the African country to supply rough from state-owned Okavango Diamond Company (ODC) to HB Botswana for five years. The partnership would operate in a similar fashion to HB’s previous supply deal with Lucara Diamond Corp, enabling Botswana to retain a share of the polished profits.

Lucara terminated its rough-supply agreement with HB in September, citing a “material breach of financial commitments” by the Belgian manufacturer as the reason for the split. That decision came on the heels of HB’s departure from cofounder and managing partner Oded Mansori, whom it has since reinstated to his original role.

There was media speculation late last year that the Botswana government was pressuring Lucara to reconnect with HB, and that the split could affect Botswana’s interest in the manufacturer. Lucara owns the Karowe mine in Botswana. The miner has since announced that it planned to form new supply deals with other vendors.

Source: DCLA

De Beers Rough Prices Slip 6% in 2023

De Beers’ prices fell last year as a prolonged oversupply in the midstream and economic challenges weighed on demand.

The company’s rough-price index, which reflects like-for-like values, dropped 6% for the 12-month period, parent company Anglo American reported Thursday.

Sales volume slipped 19% to 27.4 million carats, with the average selling price sliding 25% to $147 per carat. While the company has not published its full-year revenue, rough sales decreased 36% to $3.63 billion, according to data from De Beers’ 10 sight reports for 2023.

Output for the year was down 8% to 31.9 million carats as the company transitioned its Venetia deposit in South Africa to underground mining and processed lower-grade ore from its Canadian and Namibian sites, outweighing an increase in Botswana.

In the fourth quarter, sales volume plunged 63% year on year to 2.7 million carats, while production declined 3% to 7.9 million carats.

“De Beers offered full flexibility for rough-diamond allocations…as sightholders continued to take a cautious approach to their purchasing during the quarter as a result of the prevailing market conditions and extended cutting and polishing factory closures in India,” the company noted. “De Beers was loss-making in the second half of 2023 owing to the subdued sight sale results, reflecting conditions of cyclical lows driven by the prevailing macroeconomic environment. Whilst there has been some improvement coming into 2024, the prospects for economic growth remain uncertain and it may take some time for rough-diamond demand to fully recover.”

The miner expects to produce between 29 million and 32 million carats in 2024. However, it has cautioned that it “will assess options to reduce production in response to prevailing market conditions.”

Source: DCLA

Robust Business for Vintage Jewels at Winter Show

Seven days into the Winter Show antiques, art and design fair, there was still a steady flow of well-heeled collectors moving about the Park Avenue Armory on New York’s Upper East side. In its 70th year, the show, which ran from January 19 to 28, featured 76 exhibitors from seven countries including about nine exhibitors who specialize in collectible jewels. Several of the jewelry galleries and dealers have been longtime participants in the annual show, and nearly all were happy with business this year.

Each of the jewelry exhibitors holds a unique niche in antique and period jewels, and most say collectors were looking at a broad range of pieces that these dealers offered. As always, signed jewels were popular, but so were unsigned pieces. People were also looking for easily wearable and versatile pieces. Jewels and sketches by René Lalique were seen throughout the fair.

One of the exhibitors that had good results from pieces by the French jewelry artist was London-based Wartski, which focuses on Fabergé objects and historic European jewels, many with royal pedigree. The person behind the stand said attendees were looking for a variety of pieces from the firm’s vast collection of European and Russian jewels. Lalique was popular.

An Italian Renaissance Revival Bracelet. (Winter Show)

Benjamin Macklowe of Macklowe Gallery in New York also featured Lalique jewelry, displaying about a dozen items by the Art Nouveau jeweler at its booth this year.

“We sold across our product line. Bulgari, Cartier, Lalique and more,” he said. “Every time we sold something, regardless of the price, it was a great example of what it was.”

Macklowe’s firm handles Tiffany & Co. lamps and objects, furniture, and antique and period jewels. Among the highlights of its sales was a pair of Bulgari ruby cabochon earrings for $175,000.

A Bulgari Toi & Moi ring in platinum and yellow gold set with diamonds and a Burma ruby from Véronique Bamps. (Winter Show)

Veteran exhibitors reported feeling pleased with the outcome of the show.

This year’s installment drew “one of the best crowds” they’d ever seen, said Carrie Imberman and her brother Matthew Imberman, owners of Kentshire in New York, who have been working the Winter Show for 33 years. Like others, they say sales from the show continue after it’s over, based on the relationships they form.

Signed jewels were also popular. Among the company’s sales during the show was an Art Deco Boucheron diamond bracelet, a Hermès gold panel necklace and bombé diamond ring, and an Art Deco diamond bracelet by Cartier.

An Art Moderne gold and diamond bracelet in 18k and platinum by René Boivin. (Winter Show)

“We’ve had a good fair,” Matthew said. “We have jewels from different periods, designers and a variety of gem-set pieces. People are buying items that have a specific meaning to them.”

A La Vieille Russie has exhibited at the Winter Show almost since its inception. The company has expertise in Fabergé and other art objects of Russian origin, as well as European antique and vintage jewels. Peter Schaffer, one of the family members who lead the company, and specialist Adam Patrick were satisfied with the fair, saying they made some sales but just as importantly, they had the opportunity to meet new potential clients. For many, buying historic jewels isn’t an impulse purchase.

It’s the third time exhibiting at the Winter Show for Monaco-based dealer Véronique Bamps, who sells signed pieces from historic jewelry houses and designers. She plans to return, saying it attracts both well-cultured locals and an international crowd.

“I’ve spoken to people from a lot of countries and states,” she said. “[This show] attracts a very large crowd. And a lot of younger people who are buying pieces that they feel they could wear every day.”

Victorian ruby and diamond butterfly brooch, circa 1890. (ALVR)

For New York ladies, she added, the period is less significant. “The key is elegance when they buy jewelry,” she observed. “They fall in love, and they buy.”

Perhaps no one at the show was more pleased than Didier and Martine Haspeslagh, owners of Didier, a London-based firm that specializes in artist-designed jewels acquired on the secondary market. The couple sold several important pieces, including creations in the “five-figure” range by artists comprising Arnaldo Pomodoro, Franco Cannilla, Salvador Dali, Pablo Picasso and Sonia Delaunay, among others.

“We’ve had a very good show,” said Didier Haspeslagh. “We’ve had a number of new clients. This fair attracts people with taste, money and a need for artistic content.” People were most attracted to “big, spectacular pieces,” he continued.

18k yellow gold necklace with three abstract repoussé pendants with kinetic elements, and set with diamonds. Designed by Italian artist, Afro Basaldella, and made in the gold workshop of Mario Masenza, Rome. On offer by Didier.
(Winter Show)

Like others, Simon Teakle, whose eponymous firm is located in Greenwich, Connecticut, said that jewels by the European heritage brands were popular at the show. “There’s always a demand for signed jewels,” he noted.

Simon Teakle pair of cameo and diamond earrings by Hemmerle.
(Winter Show)

Another gallery owner who cited Art Deco jewels was James Boening, director of New York-based James Robinson, a New York-based gallery that spotlights vintage jewels, art objects, silver and flatware. He also sold items that can be worn in formal and casual surroundings. “Women are looking for jewels that are versatile,” he said. “Pieces that can be worn with jeans. Pieces that are more approachable.”  

American black opal and diamond cluster ring mounted in platinum and 14k gold, circa 1910, from James Robinson. (Winter Show)

Still, not everyone experienced successful jewelry sales at the show. Tim Martin, owner of New York-based S.J. Shrubsole specializes in vintage jewels, silver and art objects. While the other two categories did well, jewelry sales were slow, he said.

Source: DCLA

Lab Urges Caution over Surge in Undisclosed Colored Synthetics

Gemological Science International (GSI) has issued a warning to the trade after coming across a “notable increase” in jewelry set with pink, yellow and brown lab-grown diamonds posing as natural.

The jewels, which have been submitted to the lab for grading, often contain synthetic stones mixed in with natural colored diamonds, Debbie Mazar, president and cofounder of GSI, explained Tuesday. Many of the undisclosed synthetics were type IIa, with a single nitrogen atom, and ranged in size from melee to 1 carat.

Additionally, some of the lab-grown diamonds were intentionally cut to mimic natural ones, GSI noted. The GSI observed several with fractures, pinpoint clouds, polish-overs and distinct brown grain lines, features found in natural diamonds, which would potentially enable the fraudulent stones to pass standard gemological evaluation, GSI said.

“The challenge arises as most jewelry-screening equipment in the market is designed to screen white, near-colorless diamonds,” Azar explained.

The advanced technology in diamond growth is contributing to increased success by growers in replicating natural diamonds more and more, GSI added.

GSI’s warning comes on the heels of several from other labs. In December, Italian grading lab Gem-Tech cautioned that it had encountered a number of lab-grown stones circulating bearing fraudulent inscriptions from the Gemological Institute of America (GIA) for natural stones. Last month, the International Gemological Institute (IGI) examined a 6.01-carat lab-grown with a GIA laser inscription for a similarly cut natural, while the GIA reported it was taking steps to combat the recent influx of lab-growns bearing fraudulent inscriptions from the lab by offering same-day report verification.

Source: DCLA

GIA Helps in Recovery of Stolen Diamonds Worth Nearly $475K

The Gemological Institute of America (GIA) identified two diamonds, each over 4 carats, that had been stolen from a home in Colorado.

The stones were taken together with four other pieces of jewelry in June 2023, the GIA said Monday. The combined total of all six pieces is over $475,000.

A wholesale diamond dealer, who was uninvolved in the crime, sent the diamonds to the GIA for grading. When the GIA matched the stones to their reports, it found they had been reported stolen, and alerted detectives from the Boulder County Sherriff’s Office (BCSO), who were then able to use that information to make an arrest in the case, the institute explained.

“GIA often receives requests from law enforcement to help them recover GIA-graded diamonds that are reported lost or stolen,” said Christina Yates, associate general counsel responsible for this aspect of GIA’s work with law enforcement.

The GIA has trained agents with the Federal Bureau of Investigation (FBI), Customs Service and the Federal Trade Commission (FTC), in multiple countries, including the US, Canada, the UK, Belgium, Dubai, Israel and Hong Kong.

Source: DCLA

Sotheby’s Scores over $6M at Hong Kong Jewelry Auction

A sapphire and diamond ring took the top spot at a recent jewelry sale at Sotheby’s in Hong Kong, smashing its high estimate.

The piece, which contains a cushion-shaped, 17.50-carat, royal-blue Burmese sapphire surrounded by marquise-cut diamonds, sold for HKD 2.8 million ($357,226), the auction house said last week. That figure was well above its upper presale price.

In total, the January 31 Important Jewels auction brought in HKD 48.9 million ($6.3 million).

Yellow diamonds performed well at the sale, as did jewels by well-known design houses, including Graff, Cartier, Buccellati, and Van Cleef & Arpels. Sotheby’s also sold several diamonds and both green and lavender jadeite pieces with no reserve.

Here are the other four items rounding out the top five:

This cushion-shaped, 14.51-carat, fancy-intense-yellow, VS1-clarity diamond ring by Bulgari went for HKD 2.5 million ($324,751), within its presale estimate.

 

A ring set with an oval-shaped, 7.02-carat, Mozambican ruby center stone, surrounded by oval and pear-shaped diamonds, fetched HKD 2.5 million, just under its HKD 2.6 million ($332,422) upper price.

Sotheby’s sold this Graff bracelet, featuring nine cut-cornered square or rectangular-modified, fancy-intense-yellow diamonds ranging from 1.62 to 5.21 carats and 18 yellow-tinted diamonds for HKD 2.4 million ($308,513), within its estimate.

A pair of earrings, each suspending an oval ruby — one weighing 4.26 carats and the other 4.09 carats —and brilliant-cut diamonds, garnered HKD 1.9 million ($243,563) at the sale, within its presale price range.

Source: DCLA