Your Guide to

Your Guide to Heated vs Unheated Sapphires

1.13 Purple Gemstone Collection.jpg__PID:2d996add-b8e9-4ad8-8cea-b38ef589daae

Heated 1.13ct Ceylon Vivid Purple Sapphire

The most frequently asked question about sapphires and rubies here at The Sapphire Merchant is, 'What is the difference between a heated sapphire and an unheated sapphire?' This article will cover everything you need to know about this process and what it means for sapphires and rubies belonging to the Corundum family.

1. Should Sapphires be Heat Treated?

Heat treatment, a widely used and historic process in the industry, is applied to sapphires and rubies to enrich, remove, or even out their colour. In addition to altering the colour, heat can enhance the overall clarity of a sapphire. This is achieved by changing the chemical state of transition elements, through diffusion, or by dehydration (such as removing water from a material).

It is estimated that 95% of gem-quality sapphires and rubies worldwide have undergone heat treatment (or thermal enhancement, as it is sometimes referred to). Heat treatment was pioneered in the 1500s and was used to transform blue Sapphires into colourless diamond imitations or improve their colour.

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Unheated 3.00ct Opalescent Peacock Sapphire from Madagascar

2. What is the Heat Treatment Process for Sapphires?

The practice of heat treatment has evolved over the years, and an exact science now exists. Modern heat treatment involves heating the sapphire or ruby rough material to temperatures up to 1600 degrees Celcius. Heat treatment is used extensively to alter the appearance of nearly all gem-quality corundum, and this process can lighten or darken a gemstone and improve its clarity. The exact steps of this process, such as the temperature used, the length of time it is applied, and the cooling down process, vary depending on the outcome that needs to be achieved. Heat-treating gemstones is a specialised skill undertaken by a trained professional and should only be attempted in a controlled environment.

3. Can you tell if a Sapphire has been Heat Treated?

Heat treatment resembles processes that can occur in nature, and identifying heat treatment in sapphire and ruby requires experience. A gemologist can examine a gemstone under magnification to detect heat treatment, as the corundum will have certain tells that give a clue as to whether it has undergone a heating process. These observable clues directly affect the inclusions within the internal body of the gem and can include;

Fuzzy colour areas and bands

Surface pockmarks

Melted facets. Dot-like rutile "silk"

Glassy circular cracks around natural crystal inclusions

Sapphire and rubies are always inspected under high magnification, as these inclusions are much harder to observe with the naked eye. Fluorescent reactions to ultraviolet light can sometimes be observed in heat-treated blue sapphire, which, for example, often turns a faint chalky green under short-wave UV light. Even with these clues, it is only sometimes possible to determine if a sapphire or ruby has been heat-treated. However, when you shop for sapphires and rubies, you may assume that they have been heat-treated unless a laboratory report states otherwise.

How Can I Know For Sure My Sapphire is Heated or Unheated?

A laboratory report is the most comprehensive assurance confirming your sapphire's unheated or heated status. Here at The Sapphire Merchant, we have the majority of our sapphire and ruby stock assessed by a qualified gemologist at a reputable laboratory, and a report was issued stating the treatments applied to the gemstone. We prefer to use well-known gemological laboratories such as GIA (Gemological Association of America), AIGS (Asian Institute of Gemological Sciences), and GRA (Gem Research of Asia). Anything in our collection that hasn't yet undergone a laboratory assessment can be submitted to give you the guarantee you need.

GIA Report stating a sapphire is heated (under TREATMENT)

4. Are Heat Treated Sapphires Less Valuable?

Unheated sapphires and rubies, a true rarity in the gemstone world, are highly coveted by the jewellery trade, gem collectors, and connoisseurs alike. Their value is a testament to their scarcity, with high-quality unheated sapphires and rubies commanding a significant 25%—40% premium over their heated counterparts. When my clients ask me for my professional opinion on the heat treatment process, I answer: Investing in a sapphire, whether heated or unheated, is not a deciding factor for me. Both are valuable luxury choices. I chose a sapphire because I love the colour and the cut and because it feels right for me! If the sapphire is unheated, it's a bonus. It is within my standard expectation for a sapphire or ruby to be heated. Sapphires and rubies can also undergo treatments like dying, filling, diffusion, and irradiation. If a sapphire or ruby has undergone other treatments, this is a deal-breaker for me. I would not invest in or buy sapphire or ruby stock that has undergone other enhancements. It dramatically reduces the gemstone's overall value.

5. Is an Unheated Sapphire a Good Investment?

Since 1995, market prices for unheated corundum have at least tripled with rubies boasting an incredible 1200% increase. If you are buying a sapphire or ruby solely as a store of wealth, the appeal of investing lies in their stable performance. We recommend that you select an unheated natural sapphire or ruby, that has a vivid colour, minimal inclusions and a tidy cut. Additionally, origin can impact the price increase in the long term, with Myanmar (Burma), Sri Lanka (Ceylon), and Kashmir being the prestigious origins for corundum. A strong combination of these factors will ensure the best return, especially after a period of 10 years plus.

1.43ct Cornflower Blue Sapphire - The Sapphire Merchant

1.43ct Blue Sapphire Round Brilliant Cut

1.43ct Cornflower Blue Sapphire

$2,929.00

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We are thrilled to offer this lovely sapphire, part of a collection acquired from an accomplished, retired Kiwi field gemologist. His career was dedicated to volunteering at gem mining sites across Asia and Africa, where he had the unique opportunity to buy gem rough as it was discovered. Over many years, he built a sensational gem collection, each piece hand-selected with a deep knowledge of precious gemstones and what lends to their value and overall beauty. He kept his private collection under lock and key for many years but recently gave The Sapphire Merchant the unprecedented and exciting opportunity to acquire some of his most remarkable pieces. This is a unique opportunity that should not be missed.

Buying an Unheated Sapphire in New Zealand

The Sapphire Merchant is New Zealand's premier precious gemstone retailer and custom jewellery house. We travel to source and hand curate Earth's most exquisite gemstones. We are experts in precious gemstones, and we bring that expertise and passion to every single gemstone we select for our collection. When you buy a sapphire or ruby from us, you can be assured that all information regarding the gemstone is provided, and you are getting the best quality and value for your investment. Our sapphire collection is the most comprehensive in New Zealand, and we stock a sensation range of unheated and heated sapphires in many colours, cuts and carat sizes. Peruse our beautiful range and find the sapphire that has been waiting for you to discover it. From the Earth to New Zealand, to the world! Global shipping on all gems.