MORE DIAMOND FACTS

There is much more to say about Diamonds than could possibly be contained in these pages, but here are a few topics which come up most often when people are thinking about buying a diamond.

DIAMOND FLUORESCENCE

Some diamonds display ‘fluorescence’ under ultra violet light, an essential component of daylight. This is the same effect as seen in white clothes or teeth, for example, when you stand under a blue or ultra violet light.

In diamonds, fluorescence is the result of UV radiation in daylight (and other sources) causing electrons to move within the diamond’s crystal structure.

The most common type is blue fluorescence (rarely, it can be yellow or another colour). It occurs to some degree in about 25pc of diamonds, and in most cases the practical effect is negligible. If there is any visible effect of blue fluorescence it will be to make yellowish diamonds look whiter, as blue is the complementary colour to yellow.

There is no need to be concerned about fluorescence in diamonds, it is often an advantage, enhancing the whiteness of the stone, and whether or not you choose a fluorescing stone will be part of the discussion in making your final selection.

FANCY COLOURED DIAMONDS

Almost all diamonds fall within the standard D to Z colour classification, but there are what are called ‘fancy coloured diamonds’ in blues, pinks, deep yellows and even green. Some diamonds are treated to give these colours, but naturally occurring fancy coloured diamonds are very rare, much prized and a lot more costly. One of the best known mines for fancy Pink Diamonds is the Argyle Mine in Western Australia.

Colours can range from a subtle tint to strong, deep hues, and the deeper the colour, generally speaking, the more valuable the stone – in these stones brilliance and fire are less of a consideration.

As with all diamonds, very small fancy stones are unlikely to come with their own grading certificate, but it is important to have a certificate for any coloured diamonds over 0.25ct so that you can be sure of its provenance.

LABORATORY GROWN DIAMONDS

Laboratory created Diamonds have been around for a very long time, originally used in industry, gemstone quality stones have been available to consumers since the 1980s.

They are known variously as 'lab grown diamonds', 'man-made diamonds', 'created diamonds' and 'synthetic diamonds'. The latter term is often misunderstood and taken to mean 'fake'. This is wrong because these are real diamonds in every way. The preferred term in the industry is 'created', and the term we shall use here.

Like all created gemstones, lab grown diamonds have the same physical, optical and chemical properties and they are as hard as natural mined stones (at 10 on Mohs scale). They are essentially the same, but grown in a laboratory rather than in the ground, the biggest difference from natural stones being their price.

One extra benefit is that the sourcing of these diamonds is completely and unequivocally ethical. There is no possibility of any suspect mining, employment, environmental or trading practices to worry about.

However, the processes for producing diamonds in a laboratory is a complex one, and the quality of the stones is very high, so they are only less expensive in comparison to high grade diamonds, and will often be more costly than a medium grade natural diamond.

There are two processes for producing synthetic diamonds – High Pressure/High Temperature (HPHT) and Chemical Vapour Deposition (CVD). Laboratory grown diamonds have their own special grading reports so that the consumer is fully aware of what they are buying.

DIAMOND SIMULANTS

Simulated stones can be natural or man-made, the term simply means the stone is ‘similar in appearance to’ the diamond or other gemstone. More information on simulated gemstones can be found here.

Two of the best natural simulants of diamond are White Sapphire and White Zircon and each has different properties. They can clearly be distinguished from Diamonds, but they are natural stones.

White Sapphire, as all Sapphires, rates at 9 on the Mohs Scale, so is the next hardest natural gemstone to Diamond. It is a good alternative for those wanting a very large stone, but without the budget to match, although it does lack some of the fire and brilliance of Diamond.

White Zircon is one of the most brilliant non-diamond gems, but at 6-7.5 on the Mohs scale it requires more care, and may not be suitable as material for a ring to be worn every day for a lifetime.

Man-made simulants include Cubic Zirconium and Moissanite. Synthetic Moissanite (silicon carbide) is produced in a near-colourless form and its brilliance is only slightly less than a natural diamond. With a hardness of over 9 and excellent toughness, its durability also competes with a natural diamond - although I have found Princess cut Moissanite to be brittle at the corners and liable to break in a four-claw setting. Synthetic moissanite can also have a slightly greenish or greyish hue.

TREATMENTS TO ENHANCE DIAMONDS AND GEMS

This is an extract from Chapter 9 of The Engagement Ring Handbook - A Man's Guide to Getting it Right by Julie Peel.

There are a number of treatments which are routinely applied to both diamonds and gemstones to enhance their appearance, change their colours, stabilise, or otherwise improve the gem. Treatments include oiling, heating, dyeing, diffusion, irradiation, modifying inclusions in diamonds with the use of lasers as well as filling gems and diamonds with glass or resin.

Some treatments, such as filling with resin in order to deceive the customer, are not acceptable. Others have their benefits and are acceptable insofar as they are fully disclosed to the purchaser and the gem is priced accordingly. Some gemstones would hardly exist at all if it were not for common treatments, especially heat treating. An example is citrine, which is a heat treated amethyst. This occurs seldom in nature, so if it were not for heat treatment, those that were available would be much more expensive.

Any treatment which changes the colour or fundamental character of the stone will naturally affect its value and price. Some treatments are more acceptable than others and some are more obvious. Some are not permanent so the stone may degrade over time. Other treatments can make the stone less robust and so more liable to get damaged when it is worn. Unscrupulous dealers will attempt to sell treated diamonds and gemstones as natural.

All reputable stone dealers and jewellers will fully disclose relevant information about any stones they sell. This is why you must always buy your gemstones and diamonds from a reputable and knowledgeable source. Do be aware that there is no standard certification process for coloured gems as there is for diamonds, so you are reliant on the integrity of the person from whom you buy your gem.

Here’s a brief review of some of the more common treatments. A full discussion would require a book of its own, so it’s best to take expert advice.

Heat treatment

This is the most common treatment and is routinely applied to aquamarine, ruby, sapphire, tanzanite and zircon (both blue and colourless). Heating is only detectable by experts using special equipment and is usually irreversible under normal conditions.

It can lighten, darken, or completely change the colour of a stone, as well as improving clarity and brightness. Unheated rubies and sapphires will contain microscopic inclusions that show the stones have not been heated, but high quality unheated stones carry a very large price premium owing to their extreme rarity. Heat treatment brings beautiful gemstones within the reach of mere mortals.

Oiling

Oil is routinely applied to emerald, and sometimes to ruby and other stones, to fill surface fractures.

As mentioned earlier, the minerals which go to make up emerald do not occur naturally together in the Earth’s crust, so emerald formation is the result of a confluence of cataclysmic forces. As a consequence, emeralds commonly contain many inclusions, fissures and minute cracks. These can make the individual emerald fragile and give it an uneven surface even when polished. To stabilise the stone, the majority of emeralds are oiled. As it is now a standard treatment for emerald, this is not generally disclosed as it is assumed that all cut, polished and finished mined stones will be oiled. Cultured or laboratory grown emeralds (see Chapter 10) do not require oiling.

Glass fill

The objective of glass fill is to improve the appearance of the gem by filling up all the gaps and fissures with coloured glass. It is a common procedure with lower grade ruby and must always be disclosed as it makes the ruby appear better quality than it actually is.

Irradiation

In order to improve their colour, some gemstones are irradiated. This treatment is often not permanent and must be disclosed as the gem can fade or change colour again, especially when exposed for long periods to ultraviolet light.

Blue topaz is irradiated either to make the blue stronger or to change lower grade brown or dirty yellow topaz into desirable blue. Many coloured diamonds are either heat treated or irradiated in order to change the colour of the oxides they contain. So certification is important if you want to make sure you have a natural pink, for example.

Lasers

Most diamonds contain inclusions of one sort or another, which are more or less visible to the naked eye. As diamonds are composed of carbon it is not surprising that the most obvious inclusions in diamonds will be little black specks of carbon. These can spoil an otherwise perfectly good stone. One way to reduce the appearance of these black inclusions is to drill tiny holes in the diamond and target them very precisely with lasers. The lasers ‘burn’ the carbon and turn a black spec into a much less visible feather or other artefact in the stone. This is a permanent treatment and can effectively improve the quality grading of a diamond, and therefore the treatment has an impact on its price. As with any treatment, laser treatment should be disclosed in the diamond’s grading certificate.

A wide range of treatments is available for enhancing gemstones and diamonds. Most of these are entirely legitimate and accepted as long as they are declared at the point of purchase. The layperson is unlikely to be able to discern them, so do ask your jeweller about this when you are considering your purchase.

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