A close up shot of a rough, unpolished green crystal (likely emerald)

Treated or Untreated? What to Know About Precious Gemstones

A close up shot of a rough, unpolished green crystal (likely emerald)

The brilliance of precious gemstones has captivated humans for centuries. Formed under immense pressure and heat within the Earth over vast stretches of time, gems have been used throughout history in royal crowns, elaborate carvings, religious symbols, and even as medicinal treatment!

While all gemstones hold an innate beauty, there is a unique subset of gems that are particularly rare and valuable: Untreated stones. The average person might not realize that many of the stones found in commercial jewelry stores have actually been enhanced through heat treatment.

Let’s take a look at heat treatment, what it is, and why certain untreated gems are so rare and sought after.

What Are Heat-Treated Stones?

Naturally-occurring gemstones can come in a dizzying array of colors. Sometimes, though, a little nudge is needed to bring out a stone’s full potential.

Enter: The power of heat treatment. Heat is one of the necessary conditions for gemstones to form, but it can also be used to enhance stones after they’ve been mined.  

How does it work? Essentially, mined gemstones are exposed to extremely high temperatures in a carefully controlled environment. (The exact temperature and time will vary depending on the type of gemstone being treated.) The process causes the gemstone’s atoms to rearrange themselves, changing the color, clarity, and/or durability of the stone. Heat treatment is actually one of the most common gemstone treatments. It is often used on rubies, sapphires, emeralds, amethysts, and peridots, among other gems.

The Benefits of Heat Treatment

Heat treating gemstones can have a number of beneficial results on gemstones, including:

  • Changing or enhancing a gemstone’s color: Amethyst, for example, can be heated to lighten its purple hue or even transform it into a golden citrine. Sapphires can be coaxed into a richer blue, and some rubies can achieve a more vibrant red. Heat treatment can also enhance asterism in certain stones.
  • Improved clarity: Heat can sometimes melt or mend tiny fractures within a gemstone, enhancing its clarity and brilliance.
  • Increased durability: Heat treatment can make gemstones more durable and resistant to scratching and chipping. This is especially important for gemstones that are used in jewelry, as they are more likely to be exposed to wear and tear.
an emerald and diamond ring on a black background

The Allure of Untreated Stones

First of all: There is nothing wrong with bringing out a stone’s natural beauty through heat treatment. However, it’s worth noting that an emerald that has been treated to glow a rich green will be less valuable than an untreated counterpart with the same color and vibrance. Why? Because Mother Nature formed the latter option herself, without the influence of human techniques.

The rarity (and the value) of a beautiful, untreated stoned boils down to nature’s perfectionism.  The process of gemstone formation within the Earth’s crust can (and often will) introduce inclusions or uneven color distribution. For gems like emeralds and rubies, achieving a vibrant, flawless state naturally is incredibly rare. Even a tiny inclusion or a color that is a few shades too light or dark can significantly impact the value of a stone.

To unearth a large, untreated emerald in a rich verdant green, then, is like finding a treasure chest – wildly uncommon. This scarcity translates to value. That’s why you’ll often find that certain varieties of untreated gemstones, like natural Burmese rubies and natural Paraiba tourmaline, will fetch exponentially higher prices than a treated version. 

a blue and white diamond necklace on a chain

The Choice is Yours!

Whether you prefer an untreated stone or opt for a heat-treated gem is largely a personal preference. Some gemstone enthusiasts might prefer an untreated stone—but remember, there is nothing inherently wrong with a heat-treated gem!  If you love the fiery brilliance of a ruby or the captivating blue of a sapphire, a heat-treated gemstone might be a great way to find the perfect stone for your taste and budget. Just be sure to do your research and buy from a trusted jeweler.