What Makes Sapphires So Blue?

February 7th, 2014
Categorized under: Education

3.7ct Asscher Cut Natural Blue Sapphire

Second only to diamond on the Mohs scale of mineral hardness, sapphire has always been a popular choice for heirloom jewelry to last the ages.

Second only to diamond on the Mohs scale of mineral hardness, sapphire has always been a popular choice for heirloom jewelry to last the ages.

    From Victorian era jewelry to contemporary design, sapphires are a favorite gemstone for bridal pieces to last the ages. Second only to diamond in hardness, sapphires are an especially durable gemstone for jewelry to be worn on a daily basis. Where diamonds are treasured for their lack of color, sapphires are most valuable when they are rich in it – especially when they’re blue. But what makes a sapphire blue? And is one hue of blue considered necessarily better than another?

Why Sapphires Are So Blue

Sapphire is a gemstone from the mineral variety corundum and gets its blue hue from the element titanium as the crystal develops over eons, deep within the earth’s crust. Comprised namely of aluminum oxide, corundum alone is actually a transparent mineral void of color. This is where we get a ‘white sapphire’ from. But when nature adds in trace amounts of titanium oxide into the mix with just the right temperature and pressure, you get the rich blue hue sapphire is renowned for. Subtle differences in this combination, such as varying amounts of iron, can produce sapphires that are dark and inky to others that are lighter, with a cool iridescent sparkle.

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Rubies & Sapphires

Did You Know Sapphires & Rubies are of the Same Mineral?

Sapphire’s color palette doesn’t stop at just blue. Virtually every color of the spectrum, from candied pink to canary yellow, can be found within the various combinations of corundum and its elemental impurities. When corundum has enough chromium in it that it becomes red, however, it ceases to be sapphire entirely. Instead the gemstone is termed ‘ruby.’ The word corundum is actually a derivation from Tamil language’s word for ruby.

Varying Shades of Blue

There are many different shades to choose from when purchasing a sapphire: From pale cornflower to deep indigo or green and violet undertones that offer flashes of color change. Which one is considered best?  Well, as many gemologists will tell you, while a sapphire with subtle hints of violet may demand a higher price in the market, color is very much subjective. The value in color is ultimately determined by the wearer; it entirely depends on what you like.

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How Sapphires Are Graded

In searching for a sapphire, you may discover that grading is far more nuanced and relatively inconsistent a process when compared to diamond grading. Though still important factors, the old familiar 4 C’s (color, clarity, cut, and carats) do not necessarily apply in the same way here. For one, it’s especially rare to find sapphire free of natural inclusions. In fact, tiny inclusions can even lend a velvety appearance to some sapphires and increase their value, as is the case with the treasured the Kashmir variety. So ‘clarity’ seldom plays a primary factor in assessing a sapphire’s value.

Color is key is assessing a sapphire’s value. A sapphire’s color determined by its elemental make up. Sapphires with more titanium oxide and less iron will be a more vivid blue.

Color is key is assessing a sapphire’s value. A sapphire’s color determined by its elemental make up. Sapphires with more titanium oxide and less iron will be a more vivid blue.

Another key aspect in valuing gemstones is their total carat weight (TCW); that’s essentially how big they are. Nevertheless, sapphires can share an identical TCW yet vary widely in value on account of their color. Indeed, it’s almost color alone that determines a sapphires value, superseding even the cut of the gemstone.

Hue, Tone, and Saturation

Color in a sapphire is graded by its hue, tone, and saturation.  Hue refers to the gem’s inherent color. More often than not, a sapphire will exhibit a predominate color (in our case blue), with subtle undertones of another, like green, pink, or violet. Still, we refer to these gems as basically ‘blue,’ unless the other tones are significant enough to warrant a more accurate description like ‘violetish-blue’ or ‘greenish-blue.’

Hue refers to color and differences within gemstones can be very subtle.

Hue refers to color and differences within gemstones can be very subtle.

Tone is used to describe the amount or depth of color present. If two sapphires share the same hue of blue but one is endowed with more of it, that sapphire will appear darker than the other. This difference will be described as one sapphire being ‘blue’ while the other perhaps as ‘deep’ blue.

Color Gemstone Hue

Looking for differences in tone between gemstones.

Saturation refers to the extent to which the basic color is not masked by other brown or grey hues. A sapphire that is largely free of these drab hues will be described as ‘vivid,’ meaning the truest color is visible.

Grey or brown tones can subdue the saturation of color in sapphires.

Grey or brown tones can subdue the saturation of color in sapphires.

The Best Way to Gauge Color

Best way to see just how blue a sapphire is? Just look at it! Observe the gem in natural daylight as well as in various artificial lights to best determine the true color. And just like finding the perfect shade of paint, compare the gem side by side to others with similar hues. Working with a gemologist will also lend a trained eye and some expert advice to your selection.

Jeremy Dunn

Know What You’re Buying

Because there is no one entity that grades colored stones, it can be difficult to know what you’re getting. There is a common framework of assigning colored gems ‘A,’ AA,’ or ‘AAA’ ratings to denote levels of quality, but the application of such ratings is rather subjective as they are often performed by the sellers themselves. Working directly with a reputable buyer or seller will help to ensure you receive the most value in your sapphire purchase.

Dan Cavinet

Where Sapphires Originate

Sapphires come from deep within the earth’s crust in the mantle.  A mix of extreme temperature, crushing pressure, and the proper chemical elements (e.g., iron, titanium, etc.) all work together to create blue sapphire. This is a process that has taken place all over the world as sapphires are found on most every continent, from India and Southeast Asia to the Americas.

Though not yet pictured, Canadian efforts in Greenland show promise for large deposits of corundum deep under the icy earth.

Though not yet pictured, Canadian efforts in Greenland show promise for large deposits of corundum deep under the icy earth.

Additionally, sapphires from certain regions can fetch a much higher price than others. Rarity of new finds, difficulty to mine, and unique shades are all contributing factors toward increased value. Take for instance sapphires from the Kashmir valley; with a signature cornflower blue hue these gems are considered some of the most exquisite sapphires in world.

Sapphire Snowflake – Green Lake Designer and Graduate Gemologist Dan Canivet

Sapphire Snowflake – Green Lake Designer and Graduate Gemologist Dan Canivet

Owning A Natural Sapphire

In a modern world of synthetic gemstones, lab created sapphire makes its way into many products – from semiconductors to mobile phone screens – and is an economic alternative for use in fine jewelry. By selecting a natural sapphire, however, you are ensured something that is one of a kind, unmatched on this earth, and therefore more rare a possession. Similar to snowflakes, no two are the same!

More Unique Sapphires

Yogo Sapphires

Popular especially in the Pacific Northwest, Montana sapphires are a very unique shade of blue - pictured here, a pair of round brilliant cuts.

Popular especially in the Pacific Northwest, Montana sapphires are a very unique shade of blue – pictured here, a pair of round brilliant cuts.

In the mid 19th century, little blue stones served more a distraction than an opportunity to the ambitious gold miners of Montana’s Yogo gulch. For it wasn’t until 1895 that these stones were finally recognized as sapphires. Today, Montana is recognized as the largest producer of gem-quality sapphires in the nation, offering what Green Lake gemologist and jeweler Annie Van Lenten deems “some of the most beautiful sapphires [she’s] come across so far.”

Padparadscha Sapphires

Rare indeed, a Padparadscha sapphire radiates with a distinctive pink tone, akin to that of a lotus blossom.

Rare indeed, a Padparadscha sapphire radiates with a distinctive pink tone, akin to that of a lotus blossom.

Perhaps one of the rarest and most valuable varieties of sapphire isn’t even blue. The Padparadscha (that’s Sanskrit for ‘color of the lotus)’ is a distinctive yet elusive salmon pink color, with flashes of orange iridescence. Though found in parts of Vietnam and East Africa, it’s synonymous with the old world of Ceylon, or present day Sri Lanka.

For more information on how to find the very best sapphire for you, contact a Green Lake gemologist directly at: gemstones@greenlakejewelry.com

About the author:

Eric Robertson is a writer, illustrator and creative lead for Green Lake Jewelry Works.