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Gem Treatment Guide

It’s no secret that gemstones like the ones found in our collection of beautiful gemstone engagement rings take thousands, sometimes millions, of years to form. However, their journey to the jewellers doesn’t end once they have been successfully mined.

In order for gemstones to be suitable for use in jewellery – whether to enhance their look or simply to make them easier to work with – gemstones may be treated using one of a few different methods.

Read on for a look at everything you need to know about gem treatment – what it is, how treatments are carried out and how you can identify that a gem has been treated.

What is gem treatment?

Gemstone treatment is the process of exposing the rough cut stone to a variety of elements in order to achieve a desired physical change. There is a wide range of different elements that may be used to treat a gemstone – from gem heat treatment to gem water treatment – each having a different effect on the gem itself.

Elements that may be used in gem treatment include heat, gamma, light, chemicals, dye and oils.

Why are gems treated?

Gems are treated for a range of reasons, sometimes more than once.

One of the simplest reasons for gem treatment to be undertaken is that untreated gems are far more difficult to work with – by using certain gem treatment methods, gems can be made much easier for jewellers to cut and set properly.

Gems are also treated to achieve aesthetic properties, such as enhancing the colour of the gemstone or giving the gemstone a higher shine.

The nature of treatment that a gem might be exposed to depends on the type of gemstone itself. Not every gemstone can stand up to certain kinds of treatment, with some treatment methods much harsher on the gem than others.

Some treatment types achieve similar effects but are better suited to different gemstones, so it’s imperative that those carrying out gem treatments know how to select the most effective method for the stone that they are working with.

Gem treatment types

From here on in, we’ll outline the many different gem treatments used in jewellery making, alongside their treatment code and the effects that they achieve.

Bleaching (B):

This treatment uses light, heat and/or chemicals in order to remove or lighten the colour within a gemstone. This is often used to remove unwanted colour streaks in stones, leading to a more consistent colour overall.

Coating (C):

A more intense form of bleaching. This method uses heat, light and/or chemicals to alter the colour of the gemstone, either lightening or deepening the tones.

Doublet (DBL):

A thin layer of the natural stone is glued to a stronger backing material with the aim of strengthening the gem.

Dyeing (D):

Coloured dye is implanted into the stone and absorbed into the pores in order to alter the colour of the stone in a desired way.

Diffusion treatment (DS):

In an intense gem heat treatment, a stone is exposed to chemicals at very high temperatures to alter its colour and increase its shine. This treatment generally only effects the surface of the stone, with the inside retaining its original colour.

Filling (F):

This treatment is used to repair tiny cracks that occur in the stone following heat treatment, with these cracks being filled in using sodium tetraborate.

Gamma (G):

During gamma treatment, otherwise known as electron irradiation, high levels of ionising radiation are used to alter the stone’s colour.

Heating (H):

Gem heat treatment can be used to alter both the colour of the stone and its light refraction.

High Temperature/High Pressure (HTHP):

Using a combination of both high heat and pressure to alter the colour, clarity and shine of a gemstone.

Impregnation (I):

Introducing a colourless plastic agent into a porous gemstone that can be absorbed and improve the gemstone’s durability.

Lasering (L):

Using a laser to penetrate the stone at its core, reaching an inclusion – a crack, gas bubble or other matter within the gemstone. The inclusion can then be filled by a solution that either changes the look of it (for example, fills a gas bubble) or dissolves the inclusion completely.

Oiling (O):

Oiling is the practice of filling any surface-breaking cracks and holes in a stone with a colourless oil, resin or wax to fill out this imperfection and give the stone a smoother appearance overall.

Irradiation (R):

Sometimes followed by heat treatment, irradiation uses neutrons, UV rays, gamma and/or electron exposure to alter the colour of a gemstone.

Bonding (S):

This treatment uses a colourless bonding agent to enhance the colour of a gemstone.

Triplet (TPL):

A triplet is a triple-treated stone with a clear protective layer across the surface, usually formed from clear quartz, glass or hard plastic. This is generally done to achieve higher durability.

Waxing (W):

Penetrating the gemstone with colourless wax, oil or paraffin in order to improve the stone’s overall appearance.

What gems are routinely treated?

Some gems tend to be treated more frequently than others, generally in an effort to strengthen the gem or to alter the colour.

Amongst the most commonly treated gemstones are amber, citrine, tanzanite, amethyst, ruby, topaz, aquamarine, sapphire, tanzanite and tourmaline.

However, much of the antique and vintage jewellery available on the Gatsby Jewellery site is treatment free, as the technology to treat gemstones simply wasn’t available at the time of manufacture.

Amethysts are generally treated in order to enhance their clarity and give them their mesmerising purple colour. You might assume that the gemstone at the centre of this incredible 3.64 carat amethyst & 0.84 carat diamond ring has been treated using both heat and irradiation before being set, though this particular stone is actually treatment free.

Almost all rubies are treated before use in jewellery, as it’s this treatment process that gives the gemstones their famous rich red hue. However, this Art Deco natural ruby & old cut diamond trilogy ring is untreated, with its incredible colour being entirely naturally-occuring.

One of the most infrequently utilised gemstone treatments is bleaching. This treatment generally also affects the colour of the gemstone and heat treatment is considered the simplest way to achieve colour alterations. However, bleaching is more effective with some gemstones than others. This treatment is often used on pearls in order to enhance their lustre, giving them their signature high shine. This Art Deco natural pearl and old cut diamond cluster ring is a rare example of a pearl that has not been bleached to enhance its shine.

Finally, the only antique stones that were routinely treated before use in jewellery are emeralds. In fact, the Gatsby Jewellery collection boasts an extremely rare untreated and oil-free emerald – the incredible stone at the centre of our Mid-Century no oil Colombian emerald and diamond ballerina ring.

How to identify a treated gem

Around 80% of gemstones are treated in some way before they reach the retailer, whether this is out of necessity or a desire to alter the gemstone’s physical properties.

However, should you wish to identify whether or not a gemstone has been treated, there are certain physical signs that you should be looking out for.

Many treatments can be detected simply by taking a close look at the gemstone using a magnifying glass or similar tool.

Look carefully for small patches where the colour of the gemstone is uneven, either through colour bleeding or perhaps concentrations of darker colours.

You can also often tell whether or not the stone has been subject to any crack or cavity filling. Look for uneven lines or textures on the sides of the stone.

Are treated gems less valuable?

Treated gems aren’t necessarily less valuable, depending on the treatment that they have undergone and the reasons for this. This treatment and the treatment code should be disclosed to you before you make a purchase.

When purchasing a stone that you know or suspect has been treated, there are a few questions you should ask the jeweller or dealer who is selling the item to you. These are:

  • What treatments were applied to the stone?
  • What benefit did the treatment have on the stone?
  • How did the treatment affect the value of the stone?
  • Does the treatment mean that the stone requires any special care?
  • Are there any accompanying documents outlining the treatment history of the stone?

Your jeweller is required to answer these questions accurately and truthfully, otherwise the item is being sold to you under false pretences and the seller may be committing fraud.

Gemstone jewellery at Gatsby Jewellery

Whatever the gemstone you are looking for, treated or untreated, you’re sure to find the perfect gemstone jewellery for you on our site.

At Gatsby Jewellery, we pride ourselves on hand-selecting a wide range of pieces from throughout history. Whether it’s vibrant emeralds, rich sapphires or mesmerising rubies, every gemstone featured on our site has been well-maintained and looks just as beautiful as the day it was created.

For more information on any of the products on our site or to arrange a viewing, contact us today.