Diamond-Surplus Weblog

September 12, 2008

Famous Diamond #3: De Beers Diamond

Filed under: Educational Facts — diamondsurplus @ 5:44 pm
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And another famous diamond for your reading pleasure 🙂

De Beers Diamond

In March 1888, the enormous, light yellow octahedron was found in the De Beers mine

De Beers Diamond

It was cut and displayed at the Paris Exhibition in 1889.  After the removal of approximately 200 carats during cutting, its weight was 228.5 carats.

The De Beers Diamond is the 7th largest cut diamond in the world.

It was bought after being displayed in Paris, by the Maharajah of Patiala.  Cartier Paris set it in 1928 as the centrepiece of a ceremonial necklace.

In 1982, the De Beers Diamond was put up for auction at Sotheby’s, but failed to meet its undisclosed reserve.

The stone is often confused with a larger white diamond called the Imperial, Great White, or Victoria, however mathematical calculations have shown otherwise.

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September 11, 2008

Famous Diamond #2: Agra

Filed under: Educational Facts — diamondsurplus @ 4:27 pm
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Picking up from the first post of famous diamonds, here is the next in line….Agra

If I were to describe this gem in one word, it would be “captivating”.

Introducing the Agra!

Agra

Agra is the site of the Taj Mahal, one of the most beautiful buildings in the world. The diamond has a long history, with many of the earlier accounts disputed.

It has been suggested that in 1526 the Agra diamond was taken into the possession of Babur, the first Mogul Emperor, after he defeated the Rajah of Gwalior in battle.  It is recorded that Babur wore the Agra diamond in his turban.

In 1739, the Agra may have been amongst loot captured by Nadir Shah when the Persian sacked Delhi, however the gem eventually returned to India.

The diamond was reputedly smuggled to England by young military officers in around 1857, in the year of the Indian Mutiny.  However the Agra was apparently already in the possession of the Duke of Brunswick, who had paid the huge price of 348,600 francs for the stone.

Later in the 19th century, the Agra was reduced to just under 32 carats, to eliminate some black inclusions.  Even at this stage it was questioned whether the Agra was indeed the same stone that some thought it was.

More formal records indicate that Edwin Streeter purchased the Agra from Bram Hertz, with Hertz giving Streeter over £15,000 in jewels and cash in return.

Despite a lengthy lawsuit relating to the Agra, the stone remained in Streeter’s stock until 1904 when the Parisian jewellers La Cloche Freres, put the item up for sale at Christie’s in 1905.

Shortly after 1909 the gemstone was acquired by Louis Winans, son of a wealthy American railroad engineer.  Louis Winans settled in Brighton and used a local jeweller to help him create a stunning collection of coloured diamonds.

In 1990, the Agra and two other diamonds from the collection were auctioned at Christie’s.  The vendor had inherited them in 1927, and during the Second World War had buried them in the garden for safe keeping.

The Agra was certified as a fancy light pink natural coloured VSI2, and sold for £4,070,000, making it at that time, the most expensive pink diamond in the world.

Since then, the Agra has again been recut, to 28.15 carats.

What a history! Wouldn’t it be interesting if one could travel through time and watch how all these events took place? 🙂

Source: De Beers

September 10, 2008

Famous Diamonds #1: The Centenary

There are a few famous diamonds I would like to talk about but I shall not overwhelm you with its ‘sparkling’ history. Thus I shall dedicate each post to these magnificent gems. De Beers, the frontrunner in the diamond producing industry celebrated their Centenary with style. What better way than to show the world what they dug out of their backyard (pun intended, lol)

For thousands of years diamonds have been valued for their beauty and rarity, entrancing us with their fire and brilliance. Symbols of financial wealth, power and inspiration, diamonds are also a token of love and personal expression of our hopes for the future and an emblem of eternity.

So what makes a diamond famous?  Rarity is often the most important factor.  This may mean size, but extraordinary variety or intensity of colour can also make a diamond famous.  Large flawless diamonds – those with the best colour and clarity grades – are among the rarest materials on earth.

Other factors are more closely linked to the history of the individual stone. Diamonds are often named after their owner, their country or mine of origin, their colour, their shape, a special occasion or the sentiments they evoke with their unique beauty.

The Centenary

The Centenary celebrations of De Beers took place in 1988 in Kimberley, in front of a captive audience of four hundred people. These included government representatives of producer countries and other important dignitaries from the diamond industry.  Julian Ogilvie Thompson, the then Chairman, revealed that a diamond of 599 carats had been recovered from the Premier mine.

Over time, the Premier mine had produced approximately 300 stones of more than 100 carats, and nearly 25% of all the world’s diamonds over 400 carats.  These included important stones such as the Cullinan, the Niarchos, the Taylor-Burton, and the Premier Rose.

When found in 1986, only a few people knew about its discovery, and were sworn to secrecy.  The rough stone presented many difficulties in polishing it.  One of the most accomplished cutters in the world, Gabi Tolkowsky, was chosen to study and appraise the great stone.

We have recovered at the Premier mine a diamond of 599 carats which is perfect in colour – indeed, it is one of the largest top colour diamonds ever found.  Naturally it will be called the Centenary diamond.

Julian Ogilvie Thomson

He said of its top colour – “Usually you have to look into a diamond to appreciate its colour, but this just expressed itself from the surface.  That is very rare.”

Generally, however, the rough shape of the diamond meant it would be difficult to cut, and with a number of alternative routes, including cutting the diamond into several smaller stones.

In the end Tolkowsky said the diamond was to be made into one large modern-cut stone.

Tolkowsky and two other cutters, Geoff Woollett and Jim Nash, worked with hand-picked engineers in a specially constructed room in the De Beers Diamond Research Laboratory in Johannesburg.  The construction of the room itself took a year.

Meanwhile Tolkowsky studied the diamond.  He said, “From the moment I knew I was going to cut it, I became another man, a strange man.  I was looking at the stone in the day, and the stone was looking at me at night.

Kerfing by hand, Tolkowsky took 154 days to remove 50 carats, to reveal a rounded stone weighing approximately 520 carats.  After many sketches, thirteen shapes were presented to the De Beers Board, and a modified heart shape was decided upon.

After nearly a year of work, the Centenary weighed 273.85 carats.  It also had an unprecedented number of facets, with 164 on the stone and 83 on the girdle.  Two flawless pear shapes were also cut.

The Centenary is the largest modern-cut diamond in the world, and is the ultimate expression of both “fire” and “brilliance”.

Nicky Oppenheimer remarked, “Who can put a price on such a stone?”

There you go, the first of the many famous diamonds…just look at the colors bouncing off the diamond! Magnificent! 🙂

Source: De Beers

September 5, 2008

About Diamonds: A Lesson in Geology

The Origin and formation of diamonds

Ever wondered how diamonds were formed? Well, I guess not many of us really give a thought about it when we shop for a gorgeous rock (yes it is essentially just a piece of rock, albeit a shiny one, haha!) in hope to see that priceless expression on the face of our loved ones.

Since I am in the educational mode, I figured it’ll be worthwhile to know how diamonds are formed! Here’s an article I found that would help expand your geological knowledge.

Enjoy!

Since the early 1980s, a vast amount of new scientific information has become available on the origin of diamonds.

Much of this information has been obtained through the study of ‘inclusions’- natural material found within diamonds.

Diamonds were formed at least 990 million years ago, although some are estimated to be as many as 4.25 billion years old, thereby pre-dating life on this planet.

Diamonds are formed at pressures of 45-60 kbar.  A kilobar is a metric unit for measuring high pressure. This corresponds to a depth of 125-200 kilometres below the Earth’s surface where the pressure is around fifty thousand times that of atmospheric pressure at the Earth’s surface.

Some diamonds form at depths of 300-400 kilometres, or even deeper, but these diamonds are particularly rare.

Diamonds are formed at temperatures between 900°C and 1,300°C.

Formation of Kimberlite pipe

In the Earth’s upper mantle, the pressure of magma, or molten rock, cracks the surrounding rock around 125km below the Earth’s surface. The magma contains dissolved carbon dioxide, which begins to bubble and expand, either due to heat from below or reduced pressure from above.

This expansion causes the magma to erupt explosively up through the cracks, like an uncorked champagne bottle.

The resulting explosion is vastly more powerful than most volcanoes, with molten rock rising to the surface at the speed of sound, forming a ‘pipe’ through the path of least resistance to the surface.

The magma rises so quickly that diamonds do not have time to convert to graphite, which is the more stable form of carbon at the Earth’s surface. Once the diamonds cool down, they don’t have enough energy to re-form their crystal structure into graphite.

The volcanic cone eventually cools and the magma hardens into kimberlite.  It then starts to be eroded and weathered away by the elements. Eventually, it becomes almost undetectable on the surface.

Now THIS was what got my attention!

Types of Diamond Deposits

Primary deposits
Diamondiferous pipes, which are ‘pipes’ of mineral-rich volcanic rock containing diamonds, are known as primary deposits.

Diamondiferous pipes are the solidified cores of kimberlite or lamproite volcanoes.


Secondary deposits
Deposits that contain diamonds which have travelled some distance from their original source are referred to as secondary deposits.

The diamonds that are now found in Namibia, for example, have travelled over 1,000 miles from their original source in southern Africa, transported by the Orange River.

Kimberlite, lamproite and komatiite are the only types of rock known to have transported diamonds from the Earth’s interior up to the surface in significant quantities.

So there you go, a lesson in Geology! 🙂

Souce: DeBeers

September 3, 2008

Understanding The 4Cs

Filed under: Educational Facts — diamondsurplus @ 8:23 pm
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Diamonds are forever. Diamonds are a fascination. They evoke feelings of wonder and awe in the eyes of some and romance in the hearts of others.

This article below serves as a crash course in understanding the different aspects that makes a diamond what it is. I hope you’ll be somewhat educated by the end of it 🙂

Cut

Cut refers to the angles and proportions of a diamond. It is the only one of the 4Cs that is influenced by the human hand.

Diamond cutting requires great skill and training. The cutter must polish tiny surfaces known as facets onto the rough diamond. This process is what creates the facets known as the crown, culet, table, girdle and pavilion of the diamond.

To cut a diamond perfectly, a craftsman will often need to cut away more than 50% of the rough diamond.

A well-cut diamond will internally reflect light from one mirror-like facet to another and disperse and reflect it through the top of the gem. The facets, when arranged in precise proportions, will maximize the fire life and brilliance of a diamond.

A well-cut diamond will be higher in quality and value than deep or shallow-cut diamonds. Diamonds that are cut too deep or too shallow lose or leak light through the side or bottom, resulting in less brilliance and a less valuable stone.

Cut also refers to the shape of a diamond – round, square, or pear, for example.

Round diamonds are symmetrical and capable of reflecting nearly all the light that enters, so it is the most brilliant of all diamond shapes and follows specific proportional guidelines.

Non-round shapes, also known as ‘fancy shapes’ have guidelines in order that they are considered to be well-cut.

Carat

Carat refers to the weight of a diamond.

Often mistaken with size, carat it is actually a measure of weight.

The term carat is a derivative of the word carob. Carob seeds, which are surprisingly uniform in weight, were used as a reference for diamond weight in ancient civilisations. One carob seed equalled one carat.

One carat is equivalent to 200 milligrams. One carat can also be divided into 100 ‘points’.  A .75 carat diamond is the same as a 75-point or 3/4 carat diamond.

Since larger diamonds are found less frequently in nature, a single 1-carat diamond will cost more than two 1/2-carat diamonds, assuming the colour, clarity and cut are the same.

Cut and mounting can make a diamond appear larger or smaller than its actual weight.  A diamond’s setting should always optimise its beauty.

Color

Colour refers to the degree to which a diamond is colourless.

Diamonds can be found in many colours, however white-coloured or colourless diamonds remain the most popular.

Diamonds are graded on a colour scale which ranges from D (colourless) to Z. Warmer coloured diamonds (K–Z) are particularly desirable when set in yellow gold. Icy winter white coloured diamonds (D–J) look stunning set in white gold or platinum.

Colour differences are very subtle and it is very difficult to see the difference between an E and an F, for example. Therefore, colours are graded under controlled lighting conditions and are compared to a master set for accuracy.

Truly colourless stones, graded D are treasured for their rarity. Colour, however, is subjective.  The Incomparable, one of the world’s most beautiful diamonds, contains hints of brown, smokey amber and champagne colours.

Nature has also created diamonds in shades of blue, green, yellow, orange, and pink.  Red is the rarest of all. These diamonds are called ‘coloured fancies’ and are extremely rare and highly treasured.

Clarity

Clarity refers to the presence of inclusions in a diamond.

Naturally-occurring features called inclusions provide a special fingerprint within the stone. Inclusions are natural identifying characteristics such as minerals or fractures, occurring while the diamond was being formed in the Earth.

The majority of these natural birthmarks are invisible to the naked eye, yet they affect the way light is reflected and refracted within the stone.

Inclusions appear as different shapes, such as crystals, clouds or feathers. These idiosyncrasies often add to the overall character of the diamond.

Containing several birthmarks or inclusions, the Excelsior is considered one on the world’s most beautiful diamonds.

Most inclusions are not visible to the naked eye unless magnified.

To view inclusions, gemologists need to use a magnifying loupe that allows them to see a diamond at 10x its actual size.

Inclusions are ranked on a scale of perfection, known as clarity.  The clarity scale, ranging from F (Flawless) to Included (I), is based on the visibility of inclusions at a magnification of 10x.

Even with a loupe, the birthmarks in the VVS (Very, Very Slightly Included) to VS (Very Slightly Included) range can be very difficult to find. It is only when a diamond is graded ‘I’ that it is possible to see the birthmarks with the naked eye.

The position of inclusions can affect the value of a diamond and you should consider the number, size, brightness, nature and position of inclusions.

Some inclusions can be hidden by a mounting, and have little effect on the beauty or brilliance of a stone. An inclusion in the middle or top of a diamond could impact the dispersion of light, sometimes making the diamond less brilliant.

There are very few flawless diamonds found in nature, making these diamonds much more valuable.

Diamonds anyone? 🙂

Source: DeBeers

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