Everything you need to know about Heat Treated Gemstones

Guide to Heat Treated Gemstones 

If you’ve been doing your research into gemstones, then you’ve likely come across the fact that many gemstones are treated. But what does that mean? And is heat treatment an acceptable practice? Let's dive in with Gemmologist Lily, and discover everything you need to know about heat treated gemstones! 

What are Gemstone Treatments

First up let's discuss gemstone treatments as a whole. The important thing to bear in mind here is that there are different levels of gemstone treatments. Some of which are totally acceptable practices, and some treatments which definitely are not, such as resin filling (unless stated by the seller, with a reflective price).

Heat-treatment of gemstones is one of the acceptable practices. It is widely used in the industry by all manner of luxury jewellers. Most commonly, it is used with Corundum aka Rubies and Sapphires, to enhance their colour and clarity. 

What does heat treatment consist of?

Heat treatment of a Sapphire or Ruby is the recreation of what happens geologically in the ground during crystal growth. Gemstones crystallise under intense heat and pressure. If a Blue Sapphire crystal is mined from the ground and has a few inclusions or a slightly inconsistent blue colour, then the miners may deem this stone as needing a little more incubation time to maximise the clarity and colour. 

What happens then, is the crystal is essentially put into an oven at 1000+ degrees celsius, for a period of time. The amount of time they are in this environment depends on the original crystal, some sapphires will be ‘lightly heated’, and others will be heated a little more. 

Is heat treatment bad?

Heat treatment is an acceptable practice and there are two clear reasons why. The first is that all the practice does is recreate a natural process. By looking at certain inclusions, a gemmologist can tell you whether or not a Sapphire or Ruby has been heated, but they will not always be able to tell you whether or not a gemstone has been heated naturally or by human intervention. The second reason this is an acceptable practice is because there are no outside chemicals used when just heating a Ruby or Sapphire. 

There are some instances where a Sapphire may be heated with beryllium (Yellow Sapphires for example), but this isn’t a standard heat treatment practice and the Sapphire will therefore come under as a ‘beryllium treated’ stone, rather than a heat treated stone. As there are no outside chemicals used in a standard heat treatment practice, this also means the treatment is stable, meaning your Ruby or Sapphire will not alter or change in appearance over time. 

Are other gemstones besides Rubies and Sapphires heat treated? 

Yes -  most gemstones crystallise under intense heat and pressure, and therefore heat treatment can be used to alter the colour and clarity of Amethysts, Citrine and Tanzanite to name a few. 

Does a heat-treatment reduce a gemstone's value?

Heat-treated gemstones are not necessarily valued less, but unheated gemstones do carry a premium, especially if good quality. Quality is a slightly separate subject however, as regardless of whether a Ruby or Sapphire is heated or not, the quality grading system remains the same. 

What’s important to know is that the majority of gemstones on the market, and in particular Rubies and Sapphires, have had some form of heat treatment. This is to ensure you are getting the best quality stone on the market, to love and cherish for generations to come! 

Are Fenton Gemstones Heat Treated?

For the reasons discussed above the majority of our Sapphires and Rubies will have received some level of heat treatment - with the aim of always providing you with the best balance of price, colour and clarity for your gemstone!