Gemstones such as emeralds, aquamarines and kunzite need special care due their light sensitivity if we are to display them in luxury retail environments. Our guest writer, Chloe Aboud, tells us more.
When greeted by the word ‘gemstones’ – one envisages a colourful array of precious jewels, basked in a history of prestige and high value. Some do however require special care due to their sensitivity to light and heat. Let’s take a look at a few of the most prominent ones.
Diamonds, considered incredibly durable, are often coupled with the advertising slogan of ‘Diamonds are Forever’. There is, in fact, science supporting this statement.
The durability of a diamond is best seen when the stone is directly compared to its colourful counterparts on the Mohs scale, which grades minerals for scratch-resistance. Diamond is placed at the maximum rank of 10.
The Mohs scale shows how diamond tops the list of scratch-resistance when compared to other gemstones.
Interestingly, aside from diamonds, gemstones actually have no universally accepted grading system. They are often accessed – by the naked eye – for clarity and internal defects known as inclusions.
Precious or semi-precious stones can be dubbed as ‘flawless’ but as they are often formulated naturally and organically, this is seldom an attainable classification.
Emeralds, for example, are more often than not, highly ‘included’. There is virtually no emerald in existence exempt from surface fissures. One only has to examine the brilliant, 65 carat emerald brooch, once owned by Catherine the Great (sold by Christie’s New York in 2010 for $1,650,500), to see the extent of natural flaws present within the stone.
As a result, their ‘toughness’ – resistance to breakage – is ranked considerably lower to that of a diamond (7.5-8 on the Mohs scale).
The mossy and cloudy appearance of the stone is often referred to as ‘Jardin’ – the French for garden. Consequently, the majority of emeralds undergo treatment – oils and polymers fill in these surface-reaching fissures – ultimately enhancing the stone’s clarity and even its stability.
The level of oil present in the stone during inspection is tiered from 1 (none/insignificant) to 4 (moderate/significant) and has an impact on the stone’s overall value.
Caring for an emerald requires ensuring that it is not over-treated or over-cleaned, as the characteristic inclusions, when exposed to an excessive amount of heat/steam during the cleaning process, can cause the stone to shatter.
Similarly, prolonged sunlight exposure can cause the treatment oils to dry out – resulting in a cloudy, hazy appearance of the once glistening-green stone.
The appropriate care and display of gemstones is associated with their individual characteristics and durability. Interestingly, emeralds, alongside aquamarines, are the most well-known varieties of the mineral, beryl – which is, in fact, light sensitive.
Although aquamarine is considered a relatively hard stone, its pigmentation is drastically affected when exposed to sunlight. The classical, sea-blue jewel requires a cool, dark and dry storage setting. The natural tendency of beryl to fade, varies by the intensity of its colour saturation.
Therefore, emeralds, which tend to be deeply pigmented, retain more hue than their aquamarine cousins, and are consequently less prone to colour deterioration when exposed to a strong light source.
Gemstones will often undergo treatment to enhance their aesthetic appearance. Light sensitive gemstones are particularly delicate and so treatment options are highly specialised, with each individual gemstone having its own particular care requirements.
For example, heat treatment can either improve or spoil gemstone colour or clarity. The common use of a steam cleaner effectively removes dirt and oils from the surface of the gem – creating that classic ‘sparkle’. Although, in some cases, it can also force that same surface dirt and oil into any surface cracks present in the gem – creating permanent cloudiness.
JFK’s last gift to Jackie Kennedy was a kunzite and 18k gold ring, which attains its delicate colouring from a trace amount of manganese, resulting in its exquisite colour range.
With hues ranging from light pink to lavender or intense violet, it is a favourite among designers wishing to create impressive statement pieces.
However, if it is exposed to intense light (such as sunlight or a strong spotlight from a display case) or even heat, the intensity of its pigment can seriously deteriorate. Warm, soapy water works best when cleaning kunzite.
Protecting the pigmentation of light sensitive jewels is consolidated in appropriate display and storage.
Not only can spotlights from display cases project light that is too intense for some gemstones to handle, spotlights generate immense heat, which in turn, has the power to alter the integrity of the stone.
Opals are particularly vulnerable to the effects of dehydration from intense spotlights – incorrect storage can result in unsightly fissures forming on the gem’s surface.
Similarly, the light sensitive kunzite, amethyst and beryl should not be displayed in/near windows where they will be subjected to natural daylight for long periods of time.
The beauty of gemstones lies in their vibrant colour, ensuring they retain their natural pigment pertains to the longevity of the jewel and its retention of value.
Extravagant jewels, are of course, intended to evoke that ‘wow-factor’ and storing them in a cool, dark place when not being worn is key to conserving their impressiveness.
Ironically, these sparkling, elaborate statement pieces thrive in the dark – no wonder they are best suited as ‘evening wear’!
Chloe is an art historian, fine art connoisseur and art market analyst. She holds a BA in The History of Art & Architecture and French from Trinity College, Dublin. She also holds an MA in Art Business from Sotheby’s Institute of Art, London. She is a member of the Irish Association of Art Historians and has also worked with a variety of private art corporations such as Art on Superyachts and ArtRatio.