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Understanding the Difference Between Heated and Untreated Sapphires

Justin Zaroovabeli
March 11, 2024

Are you wondering about the distinction between heated and untreated sapphires? It’s simple: heated sapphires have been thermal treated to enhance their visual allure, while untreated sapphires remain as nature crafted them, inclusions and all, reflecting a rare purity. This critical difference affects not just the gemstone’s appearance, but its value and role within jewelry. Furthermore, understanding this fundamental contrast can empower consumers to make informed choices when selecting sapphires for their jewelry pieces, ensuring they align with personal preferences and ethical considerations.

Exploring the Spectrum: Heated Sapphires vs. Untreated Sapphires

orange hue untreated sapphire in a pear shape

The captivating world of sapphires is rich in beauty and allure, each gemstone narrating a unique tale. The narrative becomes more complex as we explore the differences between heated and untreated sapphires. Heated sapphires are natural sapphires that have been subjected to a thermal treatment to improve their color and clarity. This process is commonly used to enhance the gemstone’s appearance. This heat treatment is widely accepted in the industry, with almost all sapphires undergoing this process unless specifically labeled as ‘unheated’.

On the other hand, untreated sapphires are those that have been mined, cut, and polished without any enhancements, preserving their natural charm and individuality. The choice between the two is largely influenced by personal preference, wearability, and jewelry design.

The Transformation of Heated Sapphires

While all sapphires are born of the earth, not all retain their natural state. Many undergo a transformation through heat treatment, a common practice that intensifies the color and improves the clarity of the gemstones. This process targets inclusions within the sapphire, leading to their dissolution and thereby enhancing the gemstone’s color and clarity. The result? A heat-treated sapphire that boasts improved clarity and refined color, while its essential qualities remain unchanged compared to an untreated gem.

Undoubtedly, the transformation of a heated sapphire is a striking illustration of human ingenuity amplifying nature’s beauty.

The Natural Allure of Untreated Sapphires

Contrasting the transformation of natural heated sapphires is the natural allure of untreated sapphires, which are revered for their untouched beauty. These sapphires possess unique inclusions and a rarity that comes from millions of years of natural processes, making them especially coveted in their untouched state.

From the exotic terrains of Madagascar to the lush landscapes of Sri Lanka, untreated natural sapphires are sourced from various regions known for their natural sapphire deposits. Each untreated sapphire is a testament to the marvels of nature, a singular creation that has withstood the test of time to offer us a glimpse into the earth’s wondrous geological symphony.

The Heating Process Unveiled

heat treated round blue sapphires

As we delve further into the sapphire realm, understanding the heating process that forms the gemstones in today’s market becomes vital. Approximately 98% of sapphires are known to undergo some form of heat treatment. This process is widely used to improve their color and clarity. This widely adopted enhancement technique aims to alter the physical and chemical properties of sapphires to enhance their color and clarity.

But why is this process so prevalent? The answer lies in the market dynamics and consumer preferences. The heating process increases the number of gemstones considered desirable for the market, although some consumers prefer unenhanced stones for their natural qualities.

From Earth to Furnace: How Sapphires Are Heated

The journey of a sapphire from the earth to the furnace is a fascinating one. Traditionally, sapphire heating involved a clay kiln with coconut husks as fuel and a blow pipe to intensify the heat. However, modern methods use electrically operated kilns, which offer precise temperature and timing control.

The sapphires are typically heated between 1,500 and 1,800 degrees Celsius and undergo gradual cooling to avoid thermal shock. This heat treatment can improve the asterism effect, remove silk, enhance or change color, and permanently alter imperfections due to the intervalence charge transfer process. This process significantly enhances the aesthetic appeal of the gemstone, making heat treated sapphires more desirable in the market.

The Reason Behind the Heat: Market Demand and Gem Quality

The reasoning for heating sapphires stems from market demand as well as the pursuit of gem quality. Almost all commercially available sapphires, regardless of color, undergo some level of heat treatment to improve their visual qualities. This practice is widely accepted in the gemological trade, and heat treatment can significantly impact their price and value positively if done correctly.

Moreover, heated sapphires are deemed ethical and sustainable, using a larger percentage of mined sapphires and significantly reducing potential waste of gemstone resources. This highlights the importance of understanding the reasons behind the heat when choosing your sapphire.

The Rarity Factor: Why Untreated Sapphires Command Attention

a group of round untreated sapphires

While treated sapphires have a distinct allure, untreated sapphires exude an intriguing mystique. These gemstones are a true representation of the earth’s geological processes, making them rare and highly valued in the gemstone market. High-quality natural unheated sapphires are becoming more scarce, causing a significant rise in their market value. This trend suggests a growing demand for top-tier unheated sapphires. These gems can display a wide spectrum of colors, including blue, pink, yellow, green, purple, orange, and even white or colorless. The most highly prized of the sapphire family is the salmon colored Padparadscha sapphire.

Furthermore, for buyers considering their budget, the unique color variations and authenticity of unheated sapphires might justify their higher costs. The value of untreated sapphires is further enhanced by their natural inclusions, which not only serve as beauty marks but also provide insights into the gemstone’s origin. Their limited supply and natural origin contribute to the ethical value of unheated sapphires, making them attractive for investment.

Unheated Natural Gemstones: A Collector's Dream

For collectors, unheated sapphires are a dream come true. These gemstones, along with heated and unheated sapphires and other heated and unheated gemstones, are valued for their authenticity and the rarity of finding unheated gemstones that have not been chemically altered or exposed to heat treatments. The allure of an unheated sapphire lies in its natural beauty and unique inclusions that tell a story of the gemstone’s formation and its untouched character. The same can be said for unheated stones in general, as they preserve their natural essence.

Moreover, the market’s small percentage of untreated sapphires translates into a sustainable choice for collectors who are mindful of their environmental impact and are seeking pieces with potential for investment appreciation.

The Unadulterated Beauty of Untreated Sapphires

The beauty of untreated sapphires lies in their unadulterated form. These sapphires showcase a variety of colors due to natural impurities like iron, titanium, and chromium, present in the corundum mineral. Some of the colors you can find in untreated sapphires include:

  • Pink
  • Red
  • Yellow
  • White
  • Violet
  • Padparadscha (pink-orange in color)

Untreated sapphires showcase nature’s palette in all its glory.

The presence of natural rutile silk inclusions not only enhances the color of untreated sapphires but also signals that the gemstone has not been subjected to heat treatment. Each untreated sapphire maintains all its inherent qualities, making them highly valuable in their unaltered state.

Identifying Heated vs. Untreated Natural Sapphires

heat treated sapphires in different shapes

Determining whether a sapphire has undergone heating or remains untreated can be a complicated task. It often requires a third-party gemological certificate for a reliable scientific assessment from reputable laboratories. Heated sapphires tend to have more uniform and saturated colors due to the heat treatment, while untreated sapphires may display variations and unique color characteristics. However, the inclusion patterns can provide significant clues. Certain inclusions suggest whether a stone has been heated, while others indicate an untreated state.

Expert gemologists can determine whether a sapphire has been heated by examining the stone under magnification and evaluating its properties. Therefore, it’s vital for buyers to differentiate between heated and untreated sapphires, ensuring their purchase’s authenticity and avoiding potential scams.

Inclusion Patterns: Reading the Sapphire's Story

Inclusions in a sapphire tell a captivating story. These patterns, such as the presence or absence of natural incisions like rutile needles, can indicate whether a sapphire has been heated. Characteristic inclusion patterns caused by the heating process, such as missing or interrupted growth features, are often seen in heated sapphires. Halo or discoid fractures forming around inclusions in a sapphire can be a sign of heat treatment, due to the high temperatures required.

Untreated sapphires, on the other hand, contain natural inclusions, which can be as distinctive and unique as a fingerprint, indicating the gemstone’s unaltered state. These unique inclusions can also help determine the geological origin of the stone, affirming its untreated condition. Therefore, inclusion patterns can not only indicate heat treatment but can also be used to identify other treatments that a sapphire might have undergone.

The Role of Gemological Certification

Gemological certification plays a crucial role in the sapphire market by providing independent, transparent assessments. These certificates are detailed documents that verify a gemstone’s:

  • weight
  • authenticity
  • color
  • clarity
  • treatment history

These attributes are confirmed through scientific analysis. Certified gemstones give buyers assurance about the gem’s attributes and authenticity, helping to differentiate genuine stones from synthetic or treated ones and to protect against fraudulent practices.

Certificates from reputable labs detail any treatments, such as heating, fracture filling, or lattice diffusion, influencing the value and cost of a sapphire and therefore are vital for informed purchasing decisions.

Color and Clarity: Comparing Heated and Untreated Sapphires

heat treated yellow sapphire

Continuing our exploration, we shift our focus to two defining attributes of sapphires: color and clarity. Heat treatment is used to enhance the color, clarity, and overall appearance of sapphires, thereby increasing their value. Heated sapphires usually exhibit more uniform color and saturation compared to untreated sapphires, which may present natural color variations.

However, untreated sapphires maintain their original color and clarity, making each stone unique, especially when their natural color is already satisfactory and clarity is acceptable. Interestingly, fine-quality heated sapphires have shown a marginal increase in their value, reflecting the market’s appreciation for heat-treated stones.

The Impact of Heat on Blue Sapphire

The impact of heat on blue sapphires is particularly noteworthy. Heat treatment enhances the value of blue sapphires by:

  • Improving their color and clarity
  • Heating the stones at temperatures between 1,500 and 1,800 degrees Celsius to make their color more vibrant and uniform
  • Dissolving rutile needles and silk inclusions within the stones, which can obstruct the gemstone’s inherent color and affect clarity.

By improving the vibrancy and clarity of blue sapphires, heat treatment can increase the gemstone’s market value.

The Varied Palette of Untreated Natural Sapphires

While the impact of heat on blue sapphires is dramatic, it’s essential not to overlook the varied color palette of untreated sapphires. These sapphires showcase a variety of colors due to natural impurities like iron, titanium, and chromium, present in the corundum mineral. Some of the colors you can find in untreated sapphires include:

  • Pink
  • Red
  • Yellow
  • White
  • Violet

Untreated sapphires showcase nature’s palette in all its glory.

The presence of natural rutile silk inclusions not only enhances the color of untreated sapphires but also signals that the gemstone has not been subjected to heat treatment. Each untreated sapphire maintains all its inherent qualities, making them highly valuable in their unaltered state.

Ethical and Value Considerations in Choosing Sapphires

blue sapphire

The decision between heated and untreated sapphires entails more than mere aesthetic preferences or monetary considerations. It also calls for an understanding of ethical and value considerations. Disclosing the heat treatment process to buyers ensures transparency and ethical practices in the gemstone market. Moreover, buyers need to consider the care and maintenance implications of treated sapphires which may have altered durability due to advanced treatments.

Sustainability and Ethical Choices

Sustainability is a key consideration in today’s gem market. Some reasons why untreated sapphires are considered more sustainable are:

  • They are presented in their pure form, with no additional energy or materials used for enhancement.
  • Choosing untreated sapphires supports the principles of sustainable and ethical consumption by valuing natural, unaltered gemstones.
  • Ethical gemstone sellers and collectors highly value untreated sapphires for their natural and unchanged essence.

Moreover, ethically sourced sapphires adhere to stringent labor laws and environmental regulations, promoting responsible consumerism. For example, Montana sapphires are known for their vibrant colors and are responsibly sourced, following strict environmental and labor guidelines.

Investment Insights: Heated or Untreated?

From an investment perspective, unheated sapphires are more likely to appreciate in value over time due to their rarity and natural state. The high rarity of untreated sapphires, with only about 5% of the market comprising unheated natural sapphires, can make them a more valuable investment in the long term.

On the other hand, heated sapphires are more common and provide vibrant color and clarity at a lower cost, but may not appreciate in value as much as unheated sapphires. Understanding the difference between heat treatments and lattice diffusion treatments is vital for buyers, as diffusion-treated stones generally cost less and are considered less valuable than those treated by heat alone.

Untreated sapphires carry a premium in price over heated sapphires of the same color and quality, reflecting their investment appeal. Unheated blue sapphire gems that are considered ideal for investment usually possess a vivid or royal blue color, as well as fine clarity. These characteristics make them highly sought after in the gemstone market.

The Guide to Selecting Your Sapphire

Selecting a sapphire is a personal endeavor encompassing the balance of beauty and budget, comprehension of treatments beyond heating, and prioritization of personal preferences. To adhere to a budget, consider heated sapphires, which are typically more affordable, and look for competitive pricing options from online retailers or auctions. Learn about how color quality influences price with the help of a knowledgeable jeweler, and be open to sapphires with slight inclusions or smaller sizes to reduce costs.

Consider the sapphire’s end use; heated sapphires are suitable for daily wear or casual enjoyment, whereas unheated sapphires might be preferred for investment or as collector items. Ensure the seller has a good reputation to guarantee transparency concerning whether a sapphire is heated or untreated. And most importantly, let personal preference lead the decision-making process, valuing either the enhanced color and lower cost of heated sapphires or the natural authenticity of untreated sapphires.

Balancing Beauty and Budget

Striking a balance between beauty and budget is key when choosing a sapphire. While the allure of a flawless, vibrant sapphire is undeniable, it’s important to keep in mind that darker or less saturated sapphire colors are generally more affordable. Additionally, opting for settings that enhance a sapphire’s appearance, such as halo or pavé diamonds, can elevate the look of even smaller or lower-quality sapphires. This approach allows you to still enjoy the stunning beauty of a sapphire without breaking the bank.

Understanding Treatments Beyond Heating

As we’ve learned, not all sapphire treatments involve heat. Beyond heating, sapphires may undergo other treatments to enhance their appearance. Beryllium treatment is utilized to alter and intensify the hue of sapphires. This process is one of the treatments employed in the gemstone industry. Another is lattice diffusion, which involves heating sapphires to change or intensify their color significantly.

Treatments that include chemical heating or additives like glass and beryllium are considered less ethical, as they can dramatically alter the color and clarity of lower-quality sapphires. It’s important to understand these treatments to make an informed decision when purchasing a sapphire.


We’ve journeyed through the captivating world of sapphires, unraveling the intriguing tale of heated and untreated sapphires. From understanding the transformative process of heat treatment to appreciating the unadulterated beauty of untreated sapphires, we’ve delved into the multifaceted realm of these stunning natural gemstones. Whether you’re drawn to the vibrant allure of heated sapphires or the authentic charm of untreated sapphires, one thing is clear: sapphires, in all their forms, are a testament to nature’s artistic mastery. As you embark on your personal gemstone journey, may you find a sapphire that resonates with your unique story and brings a sparkle to your life.

Frequently Asked Questions

Are heat-treated sapphires valuable?

Yes, heat-treated sapphires can still hold significant value. However, untreated sapphires hold a premium due to their natural state. Properly disclosed heat-treated sapphires can still be valuable and desirable, especially if they exhibit exceptional color, clarity, and overall quality.

Are untreated sapphires more valuable?

Yes, it's true that untreated sapphires are considered more valuable due to their rarity and preservation of their natural state. While precise figures vary, it's estimated that less than 5% of mined sapphires possess the quality and clarity necessary to be deemed untreated and of gemstone quality. 

What is the difference between heat-treated and not sapphire?

Heat-treated sapphires have intensified and improved color saturation, making them more visually appealing, and the treatment can also minimize or eliminate visible inclusions, enhancing their clarity and beauty. 

Untreated sapphires are rare, thus making them more valuable and sought after.The presence of natural rutile silk inclusions not only enriches the color of untreated sapphires but also serves as an indicator that the gemstone has not undergone heat treatment. Each untreated sapphire retains its inherent qualities intact, contributing to its high value in its natural, unaltered state.

What are some ethical considerations when buying sapphires?

When purchasing sapphires, it's important to consider their origin and whether they were sourced responsibly, with fair labor practices and environmentally sustainable methods. Additionally, prioritizing transparency in the supply chain and supporting initiatives that benefit local communities and minimize environmental impact are key ethical considerations.

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