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Our guide to buying coloured gemstone engagement rings

1) Why choose colour?

Coloured gemstone engagement rings have received a real boost from the “Kate” effect, in reference the Duchess of Cambridge’s 12 carat Kashmir sapphire and diamond halo engagement ring (once owned by Diana, Princess of Wales). This phenomenon is nothing new, in 1796 Napoleon Bonaparte proposed to the future Empress Joséphine with a sapphire and diamond ring. Of course, diamonds can be found in a bedazzling array of different colours but the ‘big’ three coloured gemstones (ruby, sapphire and emerald) have been stealing the show in recent years. In fact, before De Beers gained their stranglehold on the diamond market, over 50% of engagement rings contained a coloured stone.

Uniqueness is certainly one of the key qualities of coloured gemstones. Variety is also a key part of the appeal, as coloured gemstones come in rainbow of colours, from the vivid reds of the ruby, through the deep blue, yellow, pink and green tones off sapphire, to the verdant green of emerald. Furthermore, you can add more depth and meaning with coloured stones, by incorporating your birthstone for example. You can even use coloured gemstones to send secret messages. The Victorians often did this by way of ‘acrostic’ jewellery, in which a piece containing multiple stones spelled a message using the first letter of the name of each gem.

If you are looking beyond coloured diamond, ruby, sapphire and emerald, or if your budget is more limited, consider stones such as morganite, which can be similar to a pink diamond, blue zircon, which can resemble a blue diamond. As a substitute for sapphire or ruby look at spinel or tourmaline, which are available in a wide array of colour, and tsavorite, or green garnet is a close substitute for emerald.

2) Practicality

It is important to consider the durability of a gemstone engagement ring, as some stones are significantly more fragile than others. As a rule of thumb if you are doing anything physical, including sports, exercise, D-I-Y, outdoor pursuits etc it is always worth removing an engagement ring, if possible. To assist in the assessment of how ‘hard’ a stone is, the Mohs scales was developed, in which stones are graded from 1 (talc) to 10 (diamond). Corundum (ruby and sapphire) are the hardest of coloured gemstones, at 9 on the Mohs, meaning they are the most durable and resilient. Emerald, spinel, morganite and zircon range between 7.5-8.0 and tsavorite, garnet and tourmaline 7.0-7.5. Whilst care must be taken with these stones, they will stand up to (considerate) day to day wear. It is important to remember that some stones do not respond well to humidity, changes in temperature or prolonged exposure to excessive UV light. Never clean a piece of jewellery with anything other than soap and water and a soft cloth.

 

3) Treatment & certification

Approximately 90% of all coloured gemstones have been treated in some way shape or form to improve their transparency, colour or both. There is no issue with buying a treated stone per se but the type of treatment that has been applied should be checked carefully against the certificate to ensure it is stable. With emeralds oil fracture filling of surface reaching fissures is a common practice and it substantially improves the aesthetics of the stone. It is a non-permanent treatment that can be simply re-applied (at very little cost) every 5 years or so and it does not cause any damage to the stone itself. However, filling with dyes, glues and resins can cause damage and even cleaving (or splitting) of the stone and should be avoided at all costs, as it can make a stone appear beautiful initially before disintegrating over time!

Corundum (and many other stones) are often heat treated in order to bring out their colour and enhance their clarity. This is a permanent treatment and there is no issue with it, providing it is disclosed to the seller as it has a detrimental effect on the price per carat of a stone versus an identical one that has not been treated. A good way to protect a centre stone is by careful setting, such as within a diamond halo or placing claws on any exposed corners or edges. It pays to buy stones with verified certificates from the leading gemmological laboratories, including Gübelin and SSEF in Switzerland, the GIA and AGS in the United States, HRD and IGI in Antwerp and GCS in London.

4) Setting styles for coloured gemstone engagement rings

The balancing act when it comes to setting gemstones into engagement rings involves on the one hand presenting the stone in the best possible way, whilst on the other ensuring that it is securely set into the ring itself. As discussed, halos, claws and other features can be used to hold the stone more securely in place but these do not have to be unappealing to the eye and can in fact enhance the aesthetic of the piece as an integral design element. Settings enable you to contrast different gemstones, enhance the scintillation (or ‘sparkle’) and refract light in a favourable direction.

Some examples of this include the three stone, or ‘trilogy,’ design. Emotionally this can symbolise the past, present and future or earth, wind and fire for example but practically the interplay of the light refraction between the facets of the three stones can make them appear to be larger and more beautiful. This effect can be further enhanced by the use of multiple gemstone types, such as diamond and coloured gemstones (normally ruby, sapphire and/or emerald). This technique has been commonly practiced since at least the 1600s.

5) Other factors to consider

Unlike diamonds, whose price is largely driven by the 4 ‘C’s (cut, colour, clarity & carat), the value of a coloured gemstones is mainly driven by the depth of its colour. The grading system by which clarity is measured in coloured gemstones is also far less standardised and based more upon transparency rather than clarity. With this in mind, cutters and polishers aim to produce finished stones that present the best possible tone and colour saturation, in order to maximise profit. It is also important to consider the evenness of colour saturation, known as zoning, as well as the presence, or otherwise, of secondary or bi-colours within a stone. Many emeralds for example are said to be bluish-green or yellowish-green and this can have a dramatic effect on their value. Some coloured gemstones also exhibit intriguing optical phenomena. These include chatoyancy (or the ‘cat’s-eye’ effect) and asterism (or star formations).

Origin and provenance can also be crucial factors when it comes to coloured gemstones. A fine Colombian emerald, for example, may be up to two or even three times the price a comparable fine Zambian emerald. The same is also true of Kashmir sapphire and Burmese (Myanmar) ruby versus those from east Africa. A key factor in the determination of the value of a stone also lies in who may have owned it. Gemstones that were once in the collections of famous Hollywood stars, such as Elizabeth Taylor, royalty and famous or infamous rulers can attract a premium of more than 500%.

To find out more about coloured gemstone engagement rings, get in touch with us today.