The spinel has become part of the stones of the month of August. Here are its characteristics: could you distinguish it from a ruby? ♦ ︎
In 2016 Jewelers of America and the American Gem Trade Association decided to add the spinel to the official list of birth stones in August. The spinel, in short, contends the stone scepter of the month to the peridot. In any case, the spinel is a stone that is increasingly used even in high jewelery thanks to its characteristics.
History. The spinel was also called “great impostor of the royal collections”. Yes, because many of the famous gemstones known as the Ruby of the Black Prince or the Timur Ruby which are part of the British Crown Treasure, are not rubies, but actually spinels. A 412 carat gem, which is part of the jewels of the Russian crown, and most of the red stones in the crown of Iran, which is the largest collection in the world of this red stone (almost always), are also spinels. The Samarian Spinel is, instead, the largest known spinel in the world, weighing 500 carats (about 100 grams).
Identikit. The spinel was distinguished from the ruby only in 1783 by the mineralogist Jean Baptiste Louis Rome de Lisle. From a chemical point of view, the spinel is a mineral composed of magnesium aluminate with very different characteristics compared to ruby, which for the mineralogy is instead a corundum. The spinel is less hard (a sharp ruby can scratch a spinel, but the opposite does not happen) and has a lower specific gravity. In practice, with the same volume weighs less. Moreover, it has only one index of refraction, while the birefringing ruby can have two different and distinct colors.
Colors. The main ones are red, reddish orange, deep pink, rosy red, violet and black, but also intense cobalt blue, even if very rare.
Where it is found. In Burma the best examples of spinel are extracted, in the range of red, pink, violet, orange, blue and pink. Also in Mahenge, in the south of Tanzania, gems have been recently found in great quality and with red and reddish orange color. Another important producer is Sri Lanka followed by Tajikistan, Thailand and Pakistan.
Evaluation. Although it is rare as the ruby, the price of the spinel is lower. But things are rapidly changing and the prices of the spinel are on the rise. Intense bright red is the most precious hue (hard to find), followed by red orange, rosy red and purple red. Since the spinel is usually without inclusions, transparency is very relevant in the assessment. Now that consumers can see that this stone has a lot of value, that it has a long history, they can start buying it to enrich their collection. And as the supply and quality of that supply dwindled, prices soared: from $5,000 a carat to $50,000 a carat today. At the same time, the sizes are decreasing, so while in 2007 it was easy to find a 100-carat stone, today finding a good quality 20-carat spinel is quite difficult.
Caution. There are also synthetic spinels on the market, produced in sheets through a sintering process, ie with the compaction and formation of a solid mass of material through heat or pressure.
