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What Causes The Alluring Colors Of Ruby and Sapphire?

Ruby and sapphire are members of the mineral species corundum.

The earth’s three most abundant elements are oxygen, silicon, and aluminum. All corundum varieties are made of aluminum oxide, a mixture of aluminum and oxygen. Ruby and sapphire are members of the mineral species corundum. If the dominant color of that corundum is red, it's called ruby. Although GIA uses the word "sapphire" to refer to all colors of corundum other than red, the trade and consumers often apply the single word “sapphire” to the blue variety, using “fancy sapphires” for other corundum colors. However, more accurate descriptions use their individual color names, such as yellow sapphire, pink sapphire, and orange sapphire. In this article, we will touch on ruby and blue sapphire only.

Corundum can form only under the right temperature and pressure conditions, and only in an environment with low silicon content. This makes natural corundum relatively rare.

In its purest form, corundum is colorless. Its color variations are caused by trace elements in its crystal structure. Ruby’s red is caused by chromium: The more chromium, the stronger and more saturated the red hue. Chromium can also cause red fluorescence, which adds to the color’s intensity. When the trace elements are iron and titanium, the corundum is blue sapphire. Only a few ppma (parts per million atomic) can cause the color, and the more iron the corundum contains, the darker the blue.

Color has the most impact on the value or ruby and sapphire. In standardized color terms, ruby hues range from orangy red to purplish red. The finest ruby has a pure, vibrant red to slightly purplish red hue, with vivid saturation. While blue sapphire ranges from very light to very dark violetish blue to greenish blue. The most highly valued sapphires are velvety blue to violetish blue, with medium to medium-dark tone. 

The World Famous Ruby And Sapphire

The Crimson Flame Ruby in La Jolla Jewelry Appraiser Blog
Photo courtesy of Christie's

The Crimson Flame, a 15.04-ct. untreated Burmese ruby, sold at a Christie’s Hong Kong auction in December of 2015 for $18 million. This set the world record per-carat price for a ruby sold at auction.


Blue Belle of Asia on La Jolla Jewelry Appraiser

Photo courtesy of The Jeweler Blog

Sapphire auction records were set in 2014, when a 392.52-ct. very fine blue sapphire—the so-called “Blue Belle of Asia”—sold for US$17.3 million, an astonishing $44,063 per carat. Uncovered in Sri Lanka in 1926, the gem sold for more than twice its presale estimate, reflecting the growing appreciation for top-quality gems. 


If you have loose stones or mounted jewelry and wonder what they are, we can help you with identification. At La Jolla Gem Appraisal, we have a well-equipped gemological laboratory to correctly identify natural ruby and sapphire. In case you need an appraisal report for obtaining insurance or other intended uses, they will be described by their dimensions, actual or estimated weight, color (hue, tone and intensity), clarity, attributes of cut and phenomena when applicable. Each item of jewelry is then researched for the appropriate value. You can call (858) 255-8085 or click Here to schedule appointment. See you at our office. 

Trang Pham (Jen)

Graduate Gemologist (GIA)

Applied Jewelry Professional (GIA)

Graduate Pearls (GIA)

La Jolla Gem Appraisal

7703 Fay Ave, La Jolla, CA 92037

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