Spinel is a gemstone that is unique thanks to its range of colors. The most known is a deep-red Spinel. However, the stones of a very deep-red are not suitable for jewelry purposes. Therefore, the transparent ones are the most valuable due to their similarity with Ruby.
The Difference between Spinel, Ruby and other gems
The ancients couldn’t determine a difference between Spinel and the Ruby. Therefore, we may meet many mentions of Rubies of immense size, especially in the Middle Ages.
However, Mr. De Lisle discovered the distinction between these two gems in 1783. Thus he was the first who managed to distinguish them. Before this, many Spinels considered as Rubies. The good example is the Royal Crown of England.
In fact, it is too hard to distinguish these gemstones. However, today we know how to do that.
The hardness of Spinel is 7,5-8,0/10
The hardness of Ruby is 9/10
Specific gravity of Ruby is 3,9-4,16
Specific gravity of Spinel is 3,5-3,6
Spinel is also differing from Ruby due to a different form of crystallization.
It is also essential to distinguish Spinel from Garnet. The crystals of Garnet are fusible, whereas the crystals of Spinel are infusible. Dichroism is a principal feature to identify Spinel from colored Topaz. Topaz also become electric, when heated.
Ancient Indians called Spinel “Lai Eumani.” However, its modern name probably derived from the Latin word that meant “spark,” thanks to the form of Spinel’s crystals.
By the way, there are many opinions regarding the origin of the name “Balas” (the most known variety of Spinel). Thus, Marco Polo claimed that it originates from the name of the mount Baluchani in Pegu.
The first specimens of Spinel came from India. The King of Oude possessed an enormous specimen of blue spinel. This specimen was the size of the pigeon’s egg size and possessed splendid brilliance. Furthermore, there is the evidence that two stones weighing 102,25 karats and 187 karats, respectively delivered in the UK in 1861.
The most popular varieties of Spinel, “Spinel Ruby” and “Balas Ruby” were found between Afghanistan and Tajikistan, in the region, known as Badakhshan. The locals believed that the mines of these two stones have always coexisted together.
Varieties of Spinel
There are several varieties of Spinel:
- Spinel ruby
- Balas or Balais ruby
- Almandine ruby
Colors of Spinel
In spite of commonly known red Spinel, there are many other tints of this gemstone, such as:
- Dark red for Spinel Ruby
- Rose red for Balas Ruby from the Czech Republic
- Violet for Almandine Ruby
- Orange red for Rubicelle Ruby
- Black for the rare variety called Pleonaste
- Green for Russian Spinel (Ural Mountains)
- Blue for the specimens from Sweden
The specimens of Spinel suitable for jewelry purposes principally come from Sri Lanka, Thailand, Myanmar as well as from the Czech Republic, Austria and United States (mostly in New Jersey). There are also the deposits of Spinel in Russia and Sweden.
There is a known method to obtain synthetic spinel by heating together alumina, magnesia, and boracic acid. The jewelers invented this process in the 18th century.
Credits for image to Géry Parent