Blog - Grand Auctions


In the news recently was the story of a 26.27 carat cushion cut diamond originally purchased in a Sunday sale in the 1980s for only £10. The owner always presumed it was paste and enjoyed wearing it for 30 years before finally discovering its true worth after visiting a jeweller’s. It sold for the incredible hammer price of £540,000 at Sotheby’s, London on 7th June! In this blog we take a quick look back at a few other, notable car boot sale finds.

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  • Posted by Simon Rufus

Diamond mining company Alrosa have found a 102.85 carat diamond in their Jubilee kimberlite pipe in Siberia, Russia. One of the largest diamond mines in the world, it has estimated reserves of more than 170 million carats, and has a solid reputation for large diamond finds.

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  • Posted by Simon Rufus

Featuring in Grand Auctions’ 8th June sale will be an exceptional diamond brooch with an estimated total diamond weight of 11.39 carats. It is set with a large cushion cut diamond to the centre which weighs 5.90 cts. The size and high colour grade of this diamond is what makes the brooch so special and a great deal of interest is expected on the day.

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  • Posted by Simon Rufus

In September Petra Diamonds Limited reported the recovery of an exceptional 232.08 ct white diamond at the Cullinan mine in South Africa. The stone is a D colour Type II diamond of exceptional size and clarity. This month the diamond was sold to Diacore, the diamond manufacturer, for $15,219,219 or $65,577 per carat.

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  • Posted by Simon Rufus

High Pressure High Temperature, or HPHT, describes a form of treatment that can be applied to diamonds in order to improve their colour. In this article we take a brief look at the process and explain what differentiates them from the real thing.

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  • Posted by Simon Rufus

Petra diamonds, who own the famous Cullinan mine in South Africa, have announced that they have found a 122.5 carat blue diamond there. 109 years ago the mine produced the largest piece of gem quality diamond ever discovered, the Cullinan stone. To read more about this discovery, read our blog The Cullinan II Diamond.

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  • Posted by Simon Rufus

A flawless blue diamond weighing 13.22 carats sold at Christie's auctioneers on Wednesday 14th May for a record breaking £14 million. Jean-Marc Lunel, senior international specialist of Christie's jewellery department described the stone as, 'absolutely perfect, absolutely pure externally and internally. It is almost a dream'.

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  • Posted by Simon Rufus

Diamond is one of the oldest and most fascinating gemstones. In this brief article we take a look at some of the stand out facts that have helped make diamond so precious to mankind.

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  • Posted by Simon Rufus
Ekati diamond mine Canada

As the weather men finally promise a raise in temperatures for the UK, spare a thought for those miners working at the Ekati Diamond Mine in Canada's Northwest territories. The mine is situated 120 miles south of the Arctic circle in an area covered by tundra, lakes, rivers and marshes. It is a humid subarctic continental climate with cool summers and no dry season. The average temperature typically varies from -31°C to 18°C but is rarely below -38°C or above 23°C.

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  • Posted by Simon Rufus
Kimberley diamond mine, South Africa

In the latter half of the nineteenth century, farmers, and especially their young children, would periodically find rough, alluvial diamonds. Washed up in river beds, these early diamond finds were rarely recognised for what they actually were and the gems often remained in the homestead to be used as playthings!

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  • Posted by Simon Rufus
Golden Jubilee diamond

The Golden Jubilee Diamond is the world’s largest faceted diamond. Until 1985 this title had belonged to the Cullinan I, the Star of Africa, but the discovery of a 755.5 carat piece of rough at the Premier Mine in South Africa was to change this.

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  • Posted by Simon Rufus
cut Argyle pink Jubilee diamond

A while back I posted a blog, Mining for Pink Diamonds, about the discovery in 2011 of a rough pink diamond weighing 12.76 carats at the Argyle Mine in Western Australia. It was the largest pink diamond ever found in the country. Estimated to be worth millions, the diamond was named the Argyle Pink Jubilee and was to be cut and polished in Perth, before being sold in late 2012.

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  • Posted by Simon Rufus
Cullinan I diamond

Continuing our countdown of the world’s largest cut diamonds, we have the Cullinan I in second place. The Cullinan I was one of nine major stones cut from an enormous piece of rough found in the Premier Mine in South Africa in 1905. It was the largest piece of gem quality rough ever discovered. For more information on the rough stone and how it was found, see our blog, The Cullinan II Diamond.

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  • Posted by Simon Rufus
Incomparable diamond

The Incomparable is the third largest cut diamond in the world. It was discovered as a piece of rough weighing an incredible 890 carats in the town of Mbuji Mayi in Zaire (now the Democratic Republic of Congo) in the 1980s. Incredibly, it was discovered by a young girl playing outside her uncle's house in a pile of rubble that had been discarded by a nearby diamond mine as being too bulky to be worth processing for diamonds! The little girl's uncle sold it on to some local African diamond dealers who in turn sold it to a group of Lebanese diamond buyers in Kinshasa. It was then purchased in Antwerp by De Beers and sold to Donald Zale, chairman of the board of the Zale Corporation, the Dallas-based jewellery store chain, in partnership with Marvin Samuels of the Premier Gems Corporation and Louis Glick, both prominent figures in the New York diamond industry. The finished stone was finally unveiled in November 1984 as part of Zale's 75th Diamond Anniversary.

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  • Posted by Simon Rufus
Cullinan II diamond

The Cullinan II is one of nine major diamonds cut from the largest piece of gem quality diamond ever discovered, the Cullinan stone. Late one afternoon in 1905, Mr Frederick Wells, superintendent of the prolific Premier Mine in South Africa, was making a routine inspection. He noticed something bright glinting in the mine wall several feet above him and so quickly climbed up to investigate. At first he thought that somebody was playing a practical joke and that he had been tricked by a large piece of glass. Tests quickly proved to the contrary. He had discovered a massive piece of rough diamond weighing some 3106 carats.

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  • Posted by Simon Rufus
Spirit of de Grisogono diamond

The Spirit of De Grisogono is the fifth largest diamond in the world as well as being the world’s largest cut black diamond. Mined decades ago in Central Africa, the original rough weighed some 587 carats. It was imported into Switzerland where it was cut using the Mogul cutting technique by Swiss jeweller De Grisogono. The whole process of design and execution lasted a whole year and resulted in a finished gem weighing 312.24 carats.

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  • Posted by Simon Rufus
Centenary diamond

Discovered on 17th July 1986 at the De Beers Premier Mine in Gauteng Province, South Africa, the rough stone from which the Centenary diamond was cut weighed some 599 carats. That makes it the twentieth largest rough diamond ever to come out of those mines. Once finished, it would become the world's sixth largest cut diamond. Its discovery couldn’t have been timed better for De Beers who were due to celebrate 100 years of operations in 1988. At a celebratory banquet on 11th March of that year, De Beers chairman, Julian Oglivie Thompson, announced the find to a stunned audience.

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  • Posted by Simon Rufus
Jubilee diamond

The seventh largest diamond in the world again comes from South Africa. In 1895 a rough stone shaped as an irregular octahedron and weighing 650.80 carats was unearthed in the Jagersfontein mine. The following year it was sent to Amsterdam for cutting.

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  • Posted by Simon Rufus
De Beers diamond

Weighing 234.65 carats, the De Beers Diamond is the eighth largest diamond in the world. It is cut from a huge light yellow octahedral crystal found in the De Beers Consolidated Mines not long after they opened in Kimberley, South Africa in 1888. The original crystal measured 47.6 mm through its longest axis and was some 38.1 mm square. It weighed 428.50 old carats, the pre-1913 non metric carat weight.

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  • Posted by Simon Rufus
Red Cross diamond

The ninth largest diamond in the world is called the Red Cross Diamond. The stone is a canary yellow cushion shaped diamond from the De Beers Kimberley mines in South Africa and weighs 205.07 carats. The original rough stone was found in 1901 and is said to have weighed some 375 carats.

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  • Posted by Simon Rufus
Millenium Star diamond

Over the coming weeks I’ll be having a look at some of the largest diamonds in the world. Counting down in order of size, the world’s tenth largest diamond is the Millenium Star.

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  • Posted by Simon Rufus
white gold platinum round brilliant cut diamond solitaire ring

As a firm of auctioneers and valuers, Grand Auctions deals mainly with two types of valuation. Auction valuations and insurance valuations. These two types of valuation can result in two wildly different values. One morning last week we had a client who wished to know the value of their diamond engagement ring. The ring was very attractive. It featured a round brilliant cut diamond of approximately 1.50 carats. The colour was good, around G or H on the Gemmological Institute of America’s colour grading scale. The clarity was also not bad. Around SI (slightly included) on the GIA clarity grading scale. The setting was pretty standard but the ring was very commercial and very saleable.

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  • Posted by Simon Rufus
Argyle pink Jubilee diamond

An incredible discovery was made at the Argyle diamond mine in the East Kimberley region of a remote northern corner of Western Australia a couple of weeks ago. Miners there found a rough pink diamond weighing 12.76 carats, the largest such stone found in the country. Estimated to be worth millions, the diamond has been named the Argyle Pink Jubilee and will be cut and polished over a period of ten days in Perth, before being sold later this year.

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  • Posted by Simon Rufus

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