Spinel
Hardness: 8 specific gravity 3.61-3.67
Refractive index: 1.72-1.73
Wear: excellent durability
Spinel is a beautiful and durable gem with a hardness of 8 and a refractive index close to ruby. Before the 18th century, "rose red spinel" was regarded as a kind of "Ruby", known as "balas ruby", which means Ruby from balascia, India.
The main component of spinel is MgOAl2O3. The common colors are colorless, pink, orange, red, blue, purple and black. At present, there are two famous producing areas of spinel with the highest quality, one is man sin mine in Myanmar, the other is Mahenge mine in Tanzania.
Human understanding of spinel
There are two possible origins of the name "spinel". One is from the Latin "spine", which means "thorn, bramble", which describes the common complete octahedral shape of natural spinel protoliths; the other is from the Greek "spinthalis", which means "spark, spark", which describes the unique bright red tone of spinel.
The oldest red faceted spinel in history has been found in the ancient tomb of Afghanistan in 100 B.C. and the formal mining started in 750-950 A.D. in Badakshan area of Afghanistan.
In the 10th century A.D., Al birumi, an Arab Muslim scholar, identified spinel as a variety of gemstones that could be distinguished from other gemstones, but it was not accepted by most people at that time.
In 1783, Jean Baptiste L. ROM é de l'isle, a French mineralogist, distinguished spinel from ruby for the first time in his work crystallography (Crystallography). They are obviously different in crystal structure.
The most famous "spinel" comes from the British royal family: the "Black Prince's Ruby" on the imperial state crown, weighing 170 CT. This spinel was obtained by Edward III's son Black Prince in the 14th century and has been mistaken as a ruby. In addition, the "Timur" inlaid on a British Royal Necklace Ruby "(Timur Ruby), weighing 361ct, is also a red spinel.
Colors and elements
Red is regarded as the highest quality color of "spinel", because it is most similar to ruby. However, spinel has some unique colors, such as bright red and orange red spinel, which are called flame spinel.
Red spinel is mainly colored by Cr, while blue spinel may be colored by Fe and K.
Formation and origin
Gem quality spinel crystals are often formed in marble and often coexist with rubies, so they are difficult to distinguish.
Most of the gem grade "spinels" are from alluvial deposits in Sri Lanka and Myanmar. Tanzania is also an important source of spinels, especially large-scale orange red spinels. However, the most famous Mahenge mine in Tanzania has been basically exhausted.
The spinel of man sin mine in Myanmar has a bright orange red color, which is called "Jedi spinel" by gem collectors. The spinel produced here is usually small particles less than 1ct, and rare ones more than 3CT.
Vietnam also produces high-quality red spinel, but the most special one is that Vietnam will produce "cobalt" (CO) - colored blue spinel. The Blue Spinel containing "cobalt" high has a deep and bright blue color, known as "cobalt spinel", which is very rare and very popular with gem collectors.
crystal structure
Spinel belongs to the equiaxed system (cubic), the most common crystal shape is octahedron, and it is easy to form spinel twin with concave angle. Spinel has no cleavage and good toughness.
Factors affecting value
"Spinel" is one of the gemstones whose value is most affected by color. The carat price of ordinary light spinel may only be tens of dollars, while the highest quality red spinel may be tens of thousands of dollars.
Wear and storage
The spinel has a hardness of 8. It has good durability in daily wear. It can be cleaned with warm soapy water. However, due to the possible cracks in spinel, it is necessary to be careful when using ultrasonic cleaner and steam cleaner.
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