Spinel

History
In Greek spinther means spark and in Latin spina means thorn. Spinel could derive from either term, the former referring to the gem’s lively sparkle and the latter hinting at the pointed crystal into which spinel grows by preference. For centuries, spinel was often confused with corundum, sharing many of its most desirable properties: a striking spectrum of colours, high refractive index, lively fire and resistant hardness. The confusion, usually made between red spinel and rubies, was sometimes a genuine mistake but also intentional on occasion. Only in more recent times, with the help of science, were the subtle distinctions between the two gemstone families able to be made.

 

The legendary Timur Ruby, weighing 361 carats, is probably the best-known spinel to be wrongly characterised as a ruby. Its history can be traced back to the 14th century, when it was stolen in Delhi by the Turcoman-Mongolian conqueror, Timur. From 1612, together with the Koh-i-noor diamond, it was held in India, Persia and Afghanistan, until it was presented to Queen Victoria of Great Britain in 1850. Since then, this prize jewel has been a striking member of the British Crown Jewels.

 

To this day, the largest spinel to have been unearthed is a crystal of 520 carats. It is on display in London’s Natural History Museum along with a well-formed octahedron of 355 carats.

 

Colour
The spinel family is yet another gemstone family boasting most of the colours and shades of the rainbow. Yellow spinels are not known to date.

 

Gemmological Properties
Spinel is a magnesium aluminium oxide, which usually crystallises in sharply defined octahedra. An alteration in the original quantities of magnesium or aluminium causes different colours to occur in spinels when certain foreign elements are introduced into the original chemical composition. A red spinel owes its ruby-like quality to small quantities of aluminium replaced by chromium. The different reds of spinel, however, vary from blood red through brick red to rose red. The different blues of spinel are caused by iron, titanium or zinc replacing small percentages of magnesium.

 

Mining Areas
Spinel usually shares the same places of origin as corundum. Burma, Vietnam, Tajikistan, Tanzania and Thailand are probably the best-known of these; further important spinel deposits have also been found in Sri Lanka.