In our newsletter this month:Spinel: Best Kept Secret in the Gemstone World
One of the most famous gemstones in the world is the Black Prince's Ruby, which is in the Imperial State Crown of the United Kingdom. You can see it on public display in the Tower of London (or see the photos below). This almost 5 cm long, glowing red uncut stone is estimated to weigh 170 carats. It has been in the possession of the British Royal Family since 1367.
The Black Prince's Ruby is a remarkable stone. But one of the most remarkable things about it is that it's not a ruby at all. It's a red spinel.
Prior to the scientific study of minerals, all red gems were called 'ruby'. In 1783, mineralogist, Rome de Lisle, was the first scientist to clearly distinguish the differences between true ruby and spinel. But the Black Prince's Ruby was not correctly identified as spinel until recently.
Spinel is composed of magnesium aluminate, colored by chromium and iron. It is quite hard (8 on the Mohs scale), and forms as cubic crystals like diamond. Spinel occurs in octahedral crystals, and has a complete absence of cleavage (unlike diamond). Due to spinel's excellent dispersion, spinel gems can possess vivid fire. The intensity of spinel color is partly due to the fact that spinel is singly refractive.
Spinel is usually formed as a contact metamorphic mineral in limestone. It is discovered as rolled pebbles in sand and gravel pits. Nowadays, spinel is mined primarily in Burma and Sri Lanka, usually alongside corundum (ruby and sapphire). Large stones are very rare; spinel gems weighing ten carats are practically nonexistent.
The most desirable colors that are sought after by collectors are red, hot pink and flame orange. Any spinel weighing over two carats is rare. The most valuable spinel is red or reddish-orange. One of the attractions of spinel is that it comes in a wide range of gorgeous colors. For red spinel, the finest colors tend to be similar to ruby, i.e. a rich, intense red, similar to that of a red traffic signal. However, spinel tends to be a bit more of a brick red than ruby (which is slightly more purplish). Like all gems, the most coveted are those with intense color, whilst being neither too light nor too dark. The value of red spinel tends to decline as the color diminishes into either light pink or 'garnety' (brownish) red.
So what is the great secret of spinel? The answer is that spinel is in many respects the equal of ruby and sapphire. Though ruby is slightly harder (9 on the Mohs scale), spinel contains fewer inclusions than ruby, and spinel has greater fire and brilliance. Spinel is never heated nor treated in any way; indeed, there is no known treatment for improving the color or clarity of spinel. Conversely, virtually every affordable ruby is treated in some way these days. Also, since spinel is singly refractive and ruby is doubly refractive, the primary color in red spinel appears purer and more intense than the red seen in many rubies. Yet, spinel is typically purchased for 20-50% less than ruby. That makes spinel tremendous value since prices for fine gems are rising every year.
Why then isn't spinel better known and more highly valued? The simple answer is that supply is very limited, and the jewelry industry doesn't market what it can't get. So spinel continues to be mainly a collector's stone. Here at GemSelect we are lucky to be located close to the source of the finest spinel in Burma, and our home of Chanthaburi is a major cutting and trading center for Tanzanian spinel. Although spinel supply is limited, we have better access to the supply than most gem dealers. Therefore, spinel is still a secret, but it's a secret we like to share with our customers.
Announcing Bargains of the Day
We keep a large inventory at GemSelect; typically over 7,000 gemstones. We love to buy new and interesting gems, so from time to time we need to do a bit of housecleaning and clear out some excess stock. This is your chance to pick up some excellent bargains. Each day we offer 20 gems on our bargain page at a 40% discount, with a new choice offered each day. So if you see something you like, don't hesitate!New in Gems
Our buyers are in the market every day finding the best value for our customers. Here are some of the excellent buys we've made in the last two weeks. Click on the gem names to view the latest samples.
The traditional birthstone for December is turquoise. Turquoise, known for thousands of years, has long been appreciated as a holy stone, a good-luck-charm or a talisman found in every type of jewelry. It is believed to promote good fortune, happiness and a long life. Recently, tanzanite was added to the list of birthstones for December by the American Gem Trade Association, the first time a change had been made to the birthstone list since 1912.Gemstones Worth Knowing
Each month we focus on one of the lesser known gemstones. This month's featured stone is fluorite.
Fluorite, a form of calcium fluoride, is famed for its rich variety of colors, including purple, blue, green, yellow, pink, black and reddish-orange. One of the unique properties of fluorite is that it glows when heated and fluoresces under ultraviolet light.
Flourite is quite a soft stone (scoring 4 on the Mohs scale), so is best used for pendants, brooches or earrings. It is quite a difficult stone to cut, so it needs an expert lapidary to do it justice. But the colors are splendid, and it is a relatively inexpensive gem that is available in good sized pieces. We even have a few pieces weighing over 50 carats that are suitable for collectors. For more information see our fluorite information page.Customer Questions
Every month we answer questions of general interest from our customers. Please feel free to send your questions.
A final note - If you send us email, please be assured that we answer all our email very promptly, 6 days a week. But we sometimes have problems with spam filters on the receiving end, so please adjust the settings on your mail client so you can receive mail from email@example.com.
Best wishes for the holiday season!
Your friends at GemSelect
- First Published: December-01-2006
- Last Updated: October-21-2014
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