The Myth of Princess Di and Yogo Sapphire

by David Baker

This is a story of advertising hype that has become a kind of modern-day myth. Rural Montana is a sparsely populated place with long winters. Great Britain is a third of the way around the world. At such distance it is easy to attribute to the "world" of British Royalty the glitter and romance of fairy tales. What a marketing tool--plant the idea into the mind of the female consumer that if she wears a certain piece of jewelry then perhaps a bit of the life of a princess may rub off on her.

Lady Diana's Engagement Ring

In early 1981 Prince Charles gave Diana Spencer a sapphire engagement ring. Later that year they were married and Diana became the Princess of Wales. In 1982 Intergem Corporation greatly expanded the mining, production, and marketing of Yogo sapphire using the trade name, "Royal American Sapphire." I have a copy of a newspaper article on the Yogo Sapphire Mine. The photograph above the article is of Princess Diana with the sapphire engagement ring.. Nowhere in the article does it state that the sapphire in Princess Di's engagement ring came from Yogo Gulch. However, once such an article was published it was only a small step for articles in other papers and magazines to state that Princess Di's sapphire was a Yogo. The myth grew and grew. Even today one can find some jewelers suggesting that not only is the sapphire in Princess Diana's engagement ring a Yogo sapphire, but that Yogo sapphire is in Queen Elizabeth's engagement ring.

I telephoned several jewelers and gemologists in London who are familiar with Princess Diana's engagement ring. One said that the ring had been in the shop and that he had personally examined it. The other was familiar with the ring and details of how the sapphire ring was selected. Both said that the sapphire came from Sri Lanka. The most telling comment was, "No, it's not a Yogo sapphire. They are too small."

In fact, most of the Yogo sapphires are small. The crystals grew with the elongated "barrel-shapes" that are typical for corundum in metamorphic rocks. However, the crystals formed near the base of the crust of the earth and had to be carried 50 km (or 30 miles) upwards to (just below) the surface of the earth in a hot magma that was actively dissolving them. The predominantly flat crystals in the Yogo deposit are the remains of what must have been much larger elongate crystals at depth. Most of the sapphire was dissolved by the magma, leaving the many small, flat crystals found in the Yogo dike today.

In contrast, blue sapphire formed in Sri Lanka formed in pegmatites or pegmatite-like bodies as highly metamorphosed sedimentary rocks (charnockites) underwent partial melting at mid-crustal depths. Erosion of roughly 20 km of overburden has allowed these rocks to be exposed at the surface and the placer deposits to form. Large crystals of sapphire are relatively abundant. However, the crystals tend to be heavily zoned and have abundant inclusions. Most Sri Lankan sapphire on the market is heat-treated which results in a dramatic improvement in quality.

From the many photographs of Princess Diana with her sapphire ring, one can estimate the size of the oval and thus the carat weight of the stone as in the range of 5 to 9 carats. Steve Voynick on page 163 of the 1995 edition of his book Yogo The Great American Sapphire gives the weight of the stone as 9 carats. The largest known cut Yogo sapphire is a flat hexagonal plate in the Smithsonian Museum, weighing 10.2 carats. Diana's sapphire is larger than any oval-cut Yogo sapphire; however, cut stones this size or larger from Sri Lanka are expensive, but rather common.

According to Richard Hughes on page 103 of his book Ruby & Sapphire, the question is not whether Lady Diana's sapphire came from Sri Lanka, but whether it was a heat-treated Sri Lankan sapphire.

Crown Jewels

Steve Voynick (on page 203 of the 1995 edition of his book on Yogo sapphire) states that by 1918 Queen Victoria, Princess Mary, the Duchess of York, and Kaiser Wilhelm of Germany had some Yogo sapphires in their personal gem collections and that there is a possibility that some Yogos were included in the jewel collection belonging to the British Crown. The image here is of some small, loose cut sapphires tucked away in drawers or jewelry cases. This is a far different image from the spectacular jewels in a crown worn by royalty to official functions. Which image do you think the advertiser is trying to create when he uses the terms, "Crown Jewels of England" and "royal history ... of the Yogo sapphire"?

In checking out the myth that British Royalty has Yogo sapphire in their jewelry, I wrote Leslie Field whose book The Queen's Jewels: The Personal Collection of Elizabeth II is a widely read reference on royal gemstones. Leslie Field's reply to me is dated October 5, 1998. She stated, "I am not aware of any Yogo Gulch sapphires set in any piece of jewellery belonging to a member of the British family."

Value Yogo Sapphire for its own Merits

Most of the Yogo sapphires are small--less than 1 carat. However, the cornflower blue color is choice. Lack of zonation and near absence of inclusions means that the stones have outstanding clarity. When properly cut, this gemstone gives the sensation of pleasureful color. Cornflower blue is the choicest of sapphire color.

In contrast to most sapphire on the market, Yogo sapphire is not heat-treated. It formed at a depth of 50 to 55 kilometers (or approximately 30 miles), greater than any other commercial deposit in the world.

Yogo sapphire is a gemstone that Montanans can be justifiably proud of. The demand for these stones in Montana, particularly for the larger carat sizes, far exceeds production.

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Last Updated Sept. 26, 1999 by David Baker

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