Spinel, The Mystery Stone
Modified: April 2011
by Jerry Sisk, GG; Co-Founder, Jewelry Television®
Spinel is to ruby as Salieri is to Mozart.
An odd statement to be sure, but not too far from the mark! Whenever I ask people to tell me what they know about ruby, I normally get an interesting fact or two. But ask about red spinel, and I can see their brow furrow right before a blank look crosses their face. Nearly everyone has heard of ruby, but spinel is about as well known as Salieri, whose significant musical talents were overshadowed by those of his more celebrated contemporary, Mozart.
Spinel Throughout History
Spinel has been totally eclipsed by its precious red companion in nature. To make matters worse, spinel has been confused and misunderstood by man for most of its journey throughout the corridors of history. To understand spinel better, let's deal with the past before the present.
If you look back hundreds or even thousands of years, you will notice an absence of references to spinel. Why? For starters, gems were divided by color back then. Not very scientific to be sure, but that was the standard for separation in those days. So all red gems such as spinel and garnet were placed into the category of ruby. Many famous gems, such as the Black Prince's Ruby and the Timor Ruby in the crown jewels of England, aren't rubies at all but spectacular large red spinels.
We can all be thankful for the evolution and refinement of gemology. Without this science, spinel would still be lingering in total anonymity, a fate it does not deserve. Spinel has been identified as a separate and distinct mineral for more than a century and a half, yet in all that time it has never gained the prominence or the wide-spread recognition of ruby. Although a number of factors are responsible for this outcome, supply has always been a major issue. If sufficient money were devoted to promoting and marketing spinel, it would most undoubtedly create greater demand. Over the years, the supply of spinel has never been consistent and would not be capable of sustaining such an effort. It is truly a shame, since red spinel is an excellent, less expensive alternative to ruby.
A Rainbow of Spinel Colors
I have spent a great deal of time discussing red spinel, yet spinel actually comes in every color of the rainbow. Its palette is truly exceptional. There are even colorless and black varieties of spinel. In the gem trade, the bright lively reds and cobalt blues garner the highest prices.
In addition to color, spinel has other special characteristics. In rare cases, spinel may exhibit phenomena. Star and color-change spinels are highly prized by gemstone collectors. Stars may have four or six rays, depending upon the orientation of the cut.
Durable Spinel: Jewelry and Crystals
Spinels are also excellent for use in jewelry because they are hard, tough, and more affordable than ruby or sapphire. Unfortunately, the supply of spinel limits most mass-market jewelry to smaller stones. Larger, cleaner goods are in short supply and often set in one-of-a-kind pieces.
Spinel is also prized by mineral collectors for its well-formed octahedral crystals. In rare cases, a lucky collector might even run across a fully formed cube or dodecahedron.
Separating Spinel and Corundum
It isn't difficult for a gemologist to differentiate between spinel and ruby or sapphire. Spinel may look like corundum, but it has different chemical, optical, and physical properties. Spinel is not as hard or as dense as corundum. It also has many other discrete characteristics. The most notable difference between the two is crystal structure. Spinel belongs to the cubic system and, unlike corundum, is singly refractive. The fastest and easiest way to separate the two gems is by looking for double refraction or its absence.
Chemically, spinel is a magnesium aluminum oxide, its chemical formula represented as MgAl2O4. Nature rarely creates anything quite that pure, however, and many other elements are often present in varying amounts, creating a wider range of values for many of spinel's properties. Iron, manganese, and zinc are the most common replacements for magnesium.
Spinel is found in some of the most exotic and nearly inaccessible parts of Earth. Myanmar (Burma) and Sri Lanka are two of the best-known spinel sources, but spinel is also found in Cambodia, Kenya, Madagascar, Tanzania, Thailand, and Vietnam. You may have noticed that all of these countries are also sources of corundum. Spinel is commonly found in association with ruby and sapphire.
Can spinel take its rightful place among the best that Mother Nature has to offer? Possibly, but the challenges are great. Remote locations, adverse political conditions, difficult terrain, inhospitable weather, and primitive mining techniques all work against the widespread availability and prominence of this magnificent gemstone. Unless these factors can be overcome or mitigated, spinel will continue to reign in anonymity, save among the most loyal and devoted of gemstone enthusiasts. It is to be hoped that, with time, spinel can claim greater recognition than the Salieris of the world.