Understanding Heat Treatments in Sapphires

At Anueva, jewelry and nature go hand-in-hand. Be it a salt and pepper diamond or an Evergreen tree, our hearts swell in admiration. If you’re like us, you likely share a keen appreciation for sapphires of all colors under the sun. When many people think of sapphires, the first color that often comes to mind is blue, but sapphires are available in a wide range of colors, including pink, yellow, green, purple, and even colorless. And while blue may desire to reign queen, we’ve got enough crowns to go around. 

Sapphire Heat Treatment

Regardless of your color preference, we love these magnificent gemstones for their natural beauty. Sapphires are one of the most sought-after gemstones, prized for their striking colors and exceptional durability. However, did you know that not all sapphires have their natural, bold hues? While some sapphires may have a naturally vivid color, many are treated to enhance their color and clarity. The most common treatment for sapphires is heat treatment. If you’ve ever seen a sapphire tagged as “heated” or “treated” and wondered exactly what that entails, you’ll soon know in full detail! In this blog, we’ll delve into the world of sapphire heat treatments, exploring what they are and how they can impact the gemstone’s natural properties.

What Are Heat Treatments?

Heat treatments are the oldest and most common form of sapphire enhancement that involves heating a gemstone to high temperatures to alter its physical and chemical properties. According to the academic journal, “Gems and Gemology,” the author, Nassau, explains that “[...] sapphire of natural or synthetic origin can be heat treated to improve asterism; to remove asterism or silk; to improve, add, or remove color; and even to alter imperfections.” More simply put, heat treatments are commonly used to enhance and improve the color, clarity, and overall appearance of sapphires. 

Why Are Sapphires Heat Treated?

Sapphires can contain inclusions of rutile, which are hair-like crystals that can impact the gemstone’s appearance. These rutile needles can form patterns within the crystal, and too much silk can negatively affect the sapphire’s color and clarity, making it appear dull or gray. To address this issue, heat treatment is used to dissolve the rutile needles, resulting in a more vibrant and clear sapphire with improved value. 

How Are Sapphires Heat Treated?

Sapphires are typically heat treated at temperatures between 1,500 and 1,800 degrees Celsius. During the heating process, the sapphire is placed in a furnace and heated to the desired temperature. The sapphire is then cooled slowly to prevent any thermal shock, which could cause the stone to crack or break.

The heating process can have a significant impact on the appearance of the sapphire. When a sapphire is heated, any small inclusions or impurities in the stone can be eliminated or reduced, which can improve the clarity of the stone. Additionally, heating can cause the color of the sapphire to become more vibrant and uniform, which can make the stone more valuable.

It’s important to note that not all sapphires are suitable for heat treatment. Sapphires that have inclusions that are too large or too close to the surface may be at risk of cracking or breaking during the heating process. 

Are All Sapphires Heat Treated?

Heat treatment is a widely accepted practice in the gemstone industry, and it has been used for centuries and is considered safe when performed by skilled professionals. However, it’s important to note that not all gemstones are suitable for heat treatment. 

So, when is a sapphire not recommended for heat treatment? If the sapphire already has exceptional color and clarity, heat treatment may not be necessary and could actually diminish the stone’s unique characteristics. Additionally, if heating the sapphire could cause potential damage due to the location or size of the impurities, it may not be a good candidate for heat treatment. It’s essential to carefully consider the individual characteristics of each sapphire before deciding whether or not to heat treat it. Fortunately, at Anueva, this is not a decision you’ll need to make! We responsibly source our sapphires from suppliers worldwide, and they have already been treated, if necessary. Whether you purchase a loose sapphire — heat treated or natural — you can be assured that the sapphire is the best possible version of itself. Anueva Jewelry values honesty and transparency, and all gemstones that undergo heat treatments are disclosed. 

Do Heat Treatments Affect the Price of a Sapphire?

This answer is a double-edged sword and can be answered with the dreaded, “It depends.” To further elaborate, heat treatment can significantly affect the price and value of a sapphire (for better or for worse!). If done correctly, it can enhance the gemstone’s color and clarity, resulting in a more vibrant and valuable stone. However, if performed poorly or overtreated, it can also negatively impact the stone’s value. The value of a heat-treated sapphire will ultimately depend on factors such as the quality of the original stone, the level of treatment, and the degree to which the treatment improves the stone’s appearance. In general, it’s safe to assume that a well-executed heat treatment can increase the value of a sapphire.

Natural Sapphires vs. Heat-Treated Sapphires

Is one better than the other? Of course not! It all comes down to personal preference and whether you’d like to purchase a natural sapphire or heat-treated sapphire. In any case, both are equally dazzling in their own way. 

If you value natural and rare beauty, then keep your eye out for an unheated sapphire. Unheated sapphires are considered to be rare due to their natural characteristics and the fact that they haven’t been altered or enhanced in any way; they are a true representation of the earth’s natural processes and the conditions under which the stone was formed. To compare noteworthy characteristics of heated sapphires and unheated sapphires, review the chart below for a quick overview:

Of course, this is not an exhaustive list and there may be other characteristics or factors to consider when comparing natural and heat-treated sapphires. The price and quality of a sapphire is influenced by many factors, including but not limited to whether it is natural or heat-treated. Other factors such as size, cut, and overall quality also play a significant role in determining the value of a sapphire.

Let the Sapphire Search Begin!

Now that you have a solid understanding of what heat treatments are, how they work, and when/why they're needed, you can more confidently embark on the journey to find the perfect stone! Again, it’s worth stressing that the most important factor when shopping for your dream gemstone is that you love it! At Anueva, we offer a large selection of both natural and heat-treated sapphires, and all are beautiful treasures from nature. Ready to get started? Take a step into nature's closest and explore Anueva's vast collection of ready-to-wear sapphire jewelry and loose sapphires.