Petra Diamonds

Why Diamond Grades Can Differ Between Laboratories: Understanding Colour and Clarity Variations

GIA (Gemological Institute of America) and DCLA (Diamond Certification Laboratory of Australia)

Why Diamond Grades Can Differ Between GIA and DCLA: Understanding Colour and Clarity Variations

The difference in diamond grading between laboratories like GIA (Gemological Institute of America) and DCLA (Diamond Certification Laboratory of Australia) can occur due to the subjective nature of diamond grading and variations in grading standards, tools, and methodology.

Here’s a detailed explanation of why this happens:

Example of a diamond graded GIA E VS2 vs DCLA F SI1:

1. Grading is Subjective to Some Extent

Even though labs follow international grading systems like those defined by CIBJO or GIA, colour and clarity grading involves human judgment under magnification and controlled lighting conditions. Two experienced graders may interpret borderline characteristics differently.

Colour: E and F are adjacent grades, and the difference is extremely subtle—often imperceptible to the untrained eye.
Clarity: The distinction between VS2 (Very Slightly Included 2) and SI1 (Slightly Included 1) can also hinge on size, position, nature, and number of inclusions, which may be judged differently by separate labs.

2. Different Lab Philosophies

GIA is widely considered the global benchmark for consistency and tends to be more conservative in some grading aspects, especially in colour.
DCLA, while highly respected and CIBJO-accredited (and Australia’s official diamond authority), might interpret certain characteristics differently based on their internal grading protocols.

3. Grading Conditions and Equipment

Minor differences in:

Lighting
Magnification tools
Grading environments
can affect the appearance of a diamond, especially in borderline cases.

4. Grading Date and Re-evaluation

Grading can differ if:

The diamond was graded at different times.
The diamond was repolished or slightly recut between submissions.
The grader has different levels of training or experience (even within the same lab over time).

5. Lab-to-Lab Variance Is a Known Industry Factor

Even among top labs (GIA, IGI, HRD, AGS, DCLA), 1-grade differences in colour or clarity are common and not considered errors. This is why many dealers and appraisers say a difference of one colour or clarity grade is within acceptable tolerance.

In Your Example:

GIA E VS2 vs DCLA F SI1:
- The colour difference (E vs F): within acceptable tolerance; both are considered colourless.
- The clarity difference (VS2 vs SI1): SI1 is a full grade lower, but this could be due to:
  - An inclusion judged more impactful by DCLA
  - A stricter application of clarity grading by DCLA
  - GIA possibly being more lenient on that particular clarity characteristic

Differences like GIA E VS2 and DCLA F SI1 can result from:

Subjective human interpretation
Slightly different grading standards
Borderline characteristics
Environmental and technical grading factors

For buyers or sellers, it’s important to:

Always compare certificates from top-tier labs.
Understand that 1-grade discrepancies are common.
Consider getting a professional review if there’s a significant value implication.

Graff Opens Huge Store in Las Vegas

Graff has opened its biggest store in North America, at the Fontainebleau Las Vegas luxury resort and casino.

The 3,300sq ft showroom is second only to the flagship Graff in Paris, at 3,700sq ft.

Graff, founded in 1960 by British jeweler Laurence Graff, is recognized as one of the world’s most prestigious luxury jewelers.

CEO Francois Graff (Laurence’s son) said: “The opening of our new salon at Fontainebleau Las Vegas represents a pivotal moment for Graff in North America, a testament to our continued success and commitment to expansion across the region.”

The Las Vegas store is the brand’s 10th location in North America. It has more than 50 worldwide.

The new showroom features a serpentine counter with angular displays inspired by diamond facets, a bespoke bridal area with engagement rings, wedding bands, and bridal jewelry crafted from celadon wood and chiseled glass.

To celebrate the opening, Graff has curated a special selection of high jewelry featuring rare diamonds, emeralds, rubies, and sapphires.

Source: IDEX

35 ct Kashmir Sapphire sets World Record

A 35.09-carat sapphire yesterday set a new world record for the highest per-carat price paid at auction.

The Regent Kashmir sold for HKD 74.7m (USD 9.6m), equivalent to USD 271,515 per carat, at Christie’s Hong Kong.

The same gem also set a record back in 2015, when it was sold at Christie’s Geneva for USD 7.4m, equivalent to $209,689 per carat.

That record was broken the same year by another sapphire, the 27.6- carat Jewel of Kashmir, which sold for $6.7m at Sotheby’s Hong Kong in 2015, equivalent to USD 243,703 per carat.

But the record now reverts to gem known as the Regent Kashmir, an antique cushion-shaped, unheated, royal blue sapphire set in a platinum ring with round diamonds.

“The Regent Kashmir sapphire’s record-breaking price of $271,515 per carat with a total price of $9.5m, is a landmark moment for the sapphire market – proof that the rarest gems still command unstoppable power,” said Tobias Kormind, MD and co-founder of online jeweler 77 Diamonds.

“Gemstones of this calibre continue to be sought after and go up in value.”

The sapphire sold above its low estimate (HKD 65m, USD 8.3m) but didn’t reach its high estimate (HKD 95m, USD 12.1m).

Source: IDEX

3 ct Pink Diamond could Fetch $1.6m

A fancy intense 3.03-carat pink diamond is among the highlights at Phillips’ New York Jewels Auction next month with a $1.2m to $1.6m estimate.

Other diamonds of note include a 4.43-carat oval fancy vivid yellow diamond ring (estimate $75,000 to $125,000), and a colorless emerald-cut diamond weighing 6.03 carats (F color, VVS1 clarity) with a $90,000 to $150,000 estimate. All three diamonds are set in rings.

The sale also features Etoile de Mer, a starfish-shaped sapphire, tsavorite, and diamond brooch by Jean Schlumberger, the French jewelry designer who famously revitalized Tiffany & Co during his tenure there, from 1956.

Among the 105 lots there is also a selection of signed jewels from Van Cleef & Arpels, Bulgari, Chaumet, and others. The sale is on 12 June.

Source: IDEX

392 ct Blue Belle Sapphire could Fetch $12m

The Blue Belle sapphire and diamond necklace is to lead a Christie’s New York sale next month with an estimate of $8m to $12m.

The tassel pendant features a 392.52 carat unheated, cushion modified, mixed-cut sapphire from the famed Ratnapura region of Sri Lanka, together with oval-shaped diamond terminals, and a brilliant-cut diamond neckchain, mounted in gold.

The estimate is well below the $17.6m the piece sold for at Christie’s Geneva when it last changed hands in November 2014.

The sapphire was recovered in 1926 and was sold in 1937 to was sold to British motor magnate Lord Nuffield, founder of Morris Motors.

There were reports at the time that the gem would be gifted to HM Queen Elizabeth the Queen Mother on her coronation day, though this didn’t actually happen.

“Sapphires of this caliber are extraordinarily rare,” said Rahul Kadakia, Christie’s international head of jewelry.

“This remarkable stone must be considered among the most prestigious colored gemstones to appear on the market in many years – truly worthy of any world-class collection.

Among other highlights at the Magnificent Jewels live auction on 17 June, is the Marie-Thérèse Pink Diamond, 10.38-carat kite-shaped fancy purple-pink diamond that is said to have belonged to Marie Antoinette.

It has recently been set into a contemporary ring by the Parisian jeweler Joel Arthur Rosenthal

Source: IDEX

Petra Diamonds hits all-time low as cash burn continues

Petra Diamonds is to begin discussions with financiers on refinancing a $273m bond that matures in March next year amid scepticism that the company will survive the event.

The ratings agency S&P last week downgraded the company’s credit to CCC on the increased likelihood of default, and maintained a negative outlook.

Shares in the company fell 10% today shortly after the company posted its third quarter results. Petra is now trading at a fresh all-time low and is valued at only £34m on the London Stock Exchange.

While its remaining two assets – the Cullinan and Finsch mines in South Africa – had a solid three months operationally, with a quarter to go, full year guidance has been maintained at 2.4 to 2.7 million carats.

However, the company is still burning cash.

Petra drew on a further $33m as consolidated net debt increased to $258m as of end-March, which the company put down to working capital requirements.

The truth is that the company is desperately in need of improved diamond prices, which have continued to trough this year amid economic uncertainty generated by US President Donald Trump’s on-off tariff regime.

Petra said in April that it had postponed the sale of about 200,000 carats of diamonds from the Cullinan mine near Pretoria because of the “considerable diamond market uncertainty caused by the US tariffs announcement”.

“S&P believes the company faces mounting liquidity challenges amid uncertainty regarding the recovery of the rough diamond market and approaching debt maturities in 2026, with increased likelihood of default – including distressed exchange or debt restructuring – over the next 12 months, if Petra is unable to refinance its debt maturities on time,” said analysts at Berenberg Bank in a note last week.

Commenting on the third quarter results – in which revenue fell to $42m from $106m in the comparative quarter last year (buoyed by sales from a deferred tender) – interim joint CEOs Vivek Gadodia and Juan Kemp, said Petra had experienced “a very difficult diamond market”.

They added: “We believe the steps we have taken over the past 12 months position Petra well for a successful refinancing. We will now look to commence engagements with our lenders on the refinancing of our debt maturing in early 2026.”

Source:miningmx.com

$28m Emergency Funding as Lucara Sales Dip

Lucara is drawing down up to $28m in emergency funding for its underground mine expansion after reporting a slump in Q1 earnings and lowering its revenue guidance for the full year.

The Vancouver-based miner received lender approval for the funds from its Cost Overrun Reserve Account (CORA) extending a standby undertaking, as it faces increasing financial pressure from declining revenues, operational disruptions, and a weak diamond market.

Revenue for the first quarter slipped 23 per cent to $30.3m, as heavy rainfall in January forced the company to process lower-grade stockpile material at its Karowe open pit mine, in Botswana. It sold 72,871 carats, down 22 per cent year-on-year.

“This lower revenue outlook has led management to assess the company’s ability to continue as a going concern, with concerns raised about sufficient working capital, cash flow from operations, and liquidity to meet obligations and ongoing UGP (underground mine plan) development,” Lucara said in its Q1 2025 Results.

Projected revenue for the full year has been lowered from $195m – $225m to $150m – $160m, although this figure excludes sale of the 2,488-carat Motswedi diamond that was recovered in August 2024.

Petra said lenders had approved a draw of up to $28m from the cost overrun reserve account to allow work on the underground expansion to continue.

In exchange, Nemesia, its largest shareholder, agreed to extend its shareholder standby undertaking until the project is finished.

During Q1 Lucara said it recovered six stones over 100 carats including the a 1,476 carat non-gem diamond that was sold on tender for $1.11m.

Source: IDEX

Graff and Moussaieff in UK Rich List

Laurence Graff and his son Francois are ranked 44th in the newly-published Sunday Times Rich List 2025 of Britain’s 350 wealthiest individuals.

Their worth is estimated at £3.65bn ($4.85bn), up £50m ($66m) on last year’s figure.

Laurence Graff founded the iconic Graff Diamonds in 1960 and remains chairman, aged 86. Francois, who has been involved in the family business for over 35 years, now serves as CEO.

Also in the Rich List, at number 342, is Alisa Moussaieff and family, with an estimated £342m ($454m) worth.

She is the CEO and creative director of the exclusive Moussaieff Jewellers, founded by her late husband Shlomo in 1963.

Top of the list is Gopi Hinduja and family. He chairs the Hinduja Group, a multinational conglomerate spanning automotive, oil and speciality chemicals, banking and finance, IT, cybersecurity, healthcare, trading, infrastructure project development, media and entertainment, power, and real estate, valued at £35.3bn ($46.9bn).

King Charles II is at 238, with £640m ($851m).

Source: IDEX

No Golconda Blue, but Christie’s still Raises $72m

Christie’s Geneva sold 100 per cent of lots at its Magnificent Jewels yesterday (14 May) and raised $72.3m – despite the withdrawal of the sale’s main attraction, the 23.24-carat Golconda Blue.

It carried a $35m to $50m estimate and would have been the largest fancy vivid blue diamond ever offered at auction. But consignors pulled the gem with less than three weeks’ notice, saying it would be sold a family member instead.

The new top lot was another blue, an emerald-cut 6.24-carat fancy deep blue diamond (pictured) that was sold to London-based Moussaieff Jewellers for $12.7m. Christie’s said it set an auction record price per carat for a deep blue jewel.

A fancy, vivid blue oval-shaped diamond ring of 3.68 carats set by Graff, sold for $5.8m to Lawrence Graff.

And a private collection of 21 pieces by JAR (Joel Arthur Rosenthal) sold for $7.1m, with a diamond necklace selling for $2.8m, almost five times its pre-sale estimate.

Christie’s said the auction raised $72.3m, with 77 per cent of the 115 lots selling above their high estimate. By comparison, last year’s Magnificent Jewels auction raised $54.2m.

Source: IDEX

Tanzania’s Williamson Diamonds goes totally Pink

London-listed and South Africa-active Petra Diamonds has sold its entire shareholding in Williamson Diamonds of Tanzania, plus all shareholder loans owed to it, to Pink Diamonds Investments, also of Tanzania.

Pink diamonds are known for their pink hue, ranging from light to deep rose.

The up-to-$16-million transaction has obtained Tanzanian Fair Competition Commission approval for Williamson ownership now vesting entirely with Pink, a Taifa affiliate, which is viewed as possessing the technical and financial capability to conduct operations for the benefit of stakeholders.

With more than three decades of mining-related experience, Taifa’s working relationships extend to mining majors such as De Beers, Barrick and AngloGold Ashanti, and the company is now entering a phase of exclusive ownership of an asset where about 1 100 people are employed, most of them Tanzanian.

The mine’s reserves and resources as of June 30 were reported as 37.17-million carats. With liquidity challenges continuing, further capital investment will be required.

Twenty per cent of any distributable cash generated annually by Williamson will be payable by Pink Diamonds to Petra until the selling price is met, Petra joint interim CEO Vivek Gadodia outlined in a release to Mining Weekly, in which he wished Pink all of the best as its takes over the mine, the kimberlite pipe of which was discovered by Canadian geologist John Williamson in 1940 and which led to ongoing operation since then, making it one of the world’s oldest continuous operating diamond mines. Its yield of 19-million-plus diamond carats includes a 54.5 ct Williamson pink diamond that was presented to British royalty in 1947.

Meanwhile, Petra, with the Cullinan and Finsch underground diamond mines in South Africa, is focusing on value rather than volume at a time when diamond-mining headwinds are tending to dominate the headlines and the usual sale of rough diamonds at acceptable prices is reportedly proving difficult.

This has resulted in the stockpile of rough diamonds held by De Beers, for example, rising to $2-billion, which, according to a report in the Financial Times, is the biggest hold back of rough diamonds since the financial crisis of 2008.

Source: Miningweekly