Spinel

Photo's Robert & Orasa Weldon

In the world of gemstones, people desire rarity and beauty. There is no better  way to achieve both of these goals than with nature’s treasure, a fine spinel. Once distinguished as history’s most under appreciated gemstone, spinel’s eminence is rising meteorically.

Spinel is a magnesium aluminum oxide occurring as octahedral crystals in a wide range of colors: red, orange, purple, pink, blue and black. Red spinels range from pure red to a purplish-red, not unlike the color of ruby, a gem with which it was sometimes confused. Today, collectors praise it’s rarity and pay enormous prices to obtain it..

The earliest known use of a spinel gemstone was in 100 BC, as an ornament on a Buddhist tomb in Afghanistan. It is believed that the first known systematic mining of spinel was in Afghanistan, around 750 AD. Some 500 years later, the Venetian merchant, Marco Polo, was to travel through the region, likely filling his pockets with the red gemstones - and even more likely believing them to be rubies.

According to the Oxford English Dictionary, the word spinel is derived from the early 16th century French word spinelle and the Italian spinella. The derivation of the name may be from the Latin diminutive of spina, which means thorn, believed to describe the pointed octahedral shape it is known for. In ancient times, the mines of central and southeast Asia yielded exceptionally large spinel crystals. These fine stones became known as “Balas rubies,” and some of them were the treasured property of kings and emperors, often passing through many hands as spoils of war. As a result, some of the world’s most illustrious “rubies” are actually spinel. In the 1500s and 1600s, great amounts of money we paid for so-called “balas rubies,” and there we even unscrupulous jewelers who quench crackled quartz and dyed them red; this making the world’s first fake spinels! GIA’s Robert Weldon and Cathy Jonathan writing about the notorious Cheapside Hoard, a Renaissance era treasure discovered in England in 1912, note that examples of these fake spinels - as well as real ones - were found in the hoard, (Fall 2013) Gems & Gemology. 

The most legendary spinel would invariably be the Black Prince’s Ruby. The 170 ct,  crimson-red gem set in England’s Imperial State Crown. It first appeared in the historical records of fourteenth-century Spain, and was owned by a succession of Moorish and Spanish Kings before Edward, Prince of Wales—the “Black Prince”— received the stone in 1367 as payment for a battle victory. If you travel to London, you too can see this famous jewel at the Tower of London. Entering the exhibit you are directed to a conveyor belt to view the regalia. The room is dark, with intense lights focused on the exhibits. Without much fanfare, you are soon greeted by the sight of the Black Prince's Ruby. Smoothly polished and roughly octagonal in shape, about the size of a hen’s egg, it is perched in the crown, just above the famous Cullinian II diamond. For many years, no one questioned it’s authenticity as the best known ruby in the Crown Jewels. With the study of gemology still in it’s infancy, it was only in the 1940s when the stone was finally tested and identified as a red spinel. This discovery did not diminish the stone’s intrinsic value, since its size and weight of 170 carats makes it one of the largest uncut spinels in the world, not to mention beautiful. And not to stray from the importance that royalty placed on these magnificent gems, the largest red spinel of gem quality is a 412 carat stone that is part of the Russian Crown Jewels.

According to Richard Hughes, author of Ruby and Sapphire, spinel is typically more common than ruby in deposits where both ruby and red spinel are found. Today, fine spinels come from a handful of sources. "The best red, pink and orange spinels originate from the rich gem gravels of Burma’s Mogok Stone Tract, he writes. “The best blue and violet spinels are found in Sri Lanka. Gem spinel is also found in Vietnam, the Pamir mountains of Tajikistan, Tanzania and Madagascar. Black spinel is mined in Thailand (at Bo Ploi, Kanchanaburi)."

With the evolution of gemology, measurement, attention to general observation, and a little deductive analysis it’s quite easy to separate from corundum. Spinel has a refractive index (R.I.) of 1.718. Like ruby, get’s its color from chromium, but is singly refractive. Ruby is doubly refractive (R.I. of 1.760-1.770), and exhibits pleochroism. A practiced eye will see the orange-red to purplish-red pleochroism in ruby, as well as ruby’s double refraction. These simple gemological tests separate the two gems.

As far as the general public is concerned, modern technology has helped confuse spinel’s identity even more. This is due primarily to the widespread use of synthetic spinel, a laboratory grown material that has been used an imitation for many other gems. How many consumers own class rings that are adorned with various colors of synthetic spinel? Most customers aren’t even aware that there’s a natural version of the stone. As mentioned, though, natural spinel is finally coming into its own, and standing on its own merits.

“The increase in popularity of spinel, has significantly affected prices, especially for reds,” says Deborah Yonick, reporting in Rapport. Spinel's popularity took off with the discovery of new deposits in Mahenge, Tanzania, in 2007. “For the first time, it was available in quantity, allowing manufacturers to produce sets of matching jewelry,” explains Richard Hughes. Hughes estimates that spinel prices in the past four years have appreciated by more than 500 percent! But he notes that it will be difficult to keep up that pace. “Traditionally, the finest red spinels have been about a tenth of the price of the finest rubies, so if a fine ruby can reach $200,000 a carat, $20,000 a carat is not unheard of for the finest spinel.”

Yonick notes that spinel prices have surged dramatically in the past decade, pointing out that red spinel once priced at $200 a carat wholesale now exceeds over $2,000 a carat. “Larger, finer reds and pinks over 10 carats in size could likely fetch $10,000 a carat wholesale — and beyond.” Dr. Michael S. Krzemnicki, head of the Swiss Gemmological Institute (SSEF), believes this is also, in part, due to the fact that “spinel is typically untreated, and often of exceptional size and quality.”

What better way to own a rare, beautiful, and historic treasure of nature, than with the purchase of a gleaming Spinel.

(This post appeared in Spring 2014 edition, WJA News San Diego)