Spinel

The Great Imposter

Spinel is one of the loveliest of the gem families.  Spinels are one of nature's most beautiful and truly natural creations.  They are one of the few gems that never have to be treated or enhanced.  They are moderately hard, durable stones with fine brilliance and vivid colors.

Spinel is one of the most beautiful and rare gemstone in the treasure of Mother Nature.  Its name is derived from the Latin word 'spina' that means 'thorn' in reference to the pointed shape of the stone.  Spinel is one of the less known gemstones, but it is one of the most interesting.

The strongest reasons for buying a spinel are its rich, brilliant array of colors and its surprising affordability.

Spinel Jewelry

Today this fascinating gemstone is used for making lovely jewelry items - most often from 18K yellow gold.  Silver and white gold are used less as yellow gold complements the beauty of the stone more.  This gemstone is very well paired with diamonds.

Spinel is a very hard and durable gemstone as it rates 8 Mohs on the hardness scale.  Typically spinel is not treated or enhanced.  Therefore, apart from general gemstone care no other specific precautions are required.  Jewelry made using this stone can be worn daily.  However, the stone should not be taken for granted, i.e., general care is appropriate.  It is usually safe to clean spinel in an Ultra Sonic Cleaner, and usually safe to use a steamer, and always safe to use Ionic Cleaners and/or warm, soapy water and a soft brush to clean your spinel jewelry.

It should come as no surprise that spinel remains a favorite alternative to rubies and sapphires.  An equivalent looking spinel displays all the beauty, rarity, color, history, and luster of a ruby or sapphire; at a fraction of the price.  Spinel's failure to draw widespread recognition among consumers is that it's actually rarer than rubies-too rare for the contemporary market to offer the gem in abundant volume.  Yet, with a hardness of 8 on the Moh's scale, with no cleavage, spinel is beautifully and safely set in fine jewelry.

History

Spinel is the great imposter of gemstone history - red spinel for ruby, and blue spinel for sapphire.

In Burma, where some of the most beautiful colors are mined, spinel has been recognized as a separate gem species since 1600.  But in other countries the masquerade continued for hundreds of years.  The stage for confusion was probably set by the fact that modern gemology was a latecomer to the science field.  The royal gem experts of yesteryear were often unable to distinguish between the spinel and actual rubies (and sapphires) because they appeared remarkably similar and are found in the same locations.  Although Burma identified the gem type in 1587, it wasn't until the 19th century that gemologists widely began to distinguish the difference between the two cousins.  Prior to this spinel was classified as a ruby and shared the ruby's reputed medicinal and prophetic power.

Historically, fine red spinels were esteemed as much as ruby, and sometimes even more.  Next to ruby and the rare red diamond, red spinel is the most expensive of all red gems.  At first glance, it is almost impossible to distinguish between the two.

Many crown jewels of royal families had spinel instead of the precious gemstone ruby.  The Black Prince's ruby set in the British Imperial State Crown has less valuable red spinels in place of expensive Rubies.  This mistake or well-planned act of the jeweler is still an enigma.  Both these gemstones are very similar to one another chemically and also in physical properties.  Thus, red spinel is considered a poor man's ruby.

With red spinel's ruby-like appearance deceiving some of the brightest minds of yesteryear, it naturally presents itself as the substitute of choice for ruby.  In fact, the only thing really holding back red spinel's recognition is the fact that is rarer than ruby - too rare to make it into the modern jewelry market in any substantial volume.

Gemological / Mineralogical Identity

Gem spinel is a magnesium aluminum oxide (MgAl2O4), while ruby (corundum) is an aluminum oxide (Al2O3).  In deposits where both ruby and red spinel are found, spinel is typically more common than ruby.  When both magnesium and aluminum are present, spinel grows.  Only after the magnesium is exhausted, does ruby get a chance to crystallize.  Both ruby and red spinels owe their color to the same Cr+3 ion.

Spinel occurs as well formed crystals (octahedrons) in igneous rocks, metamorphic rocks and in contact metamorphosed limestone.  Spinels and rubies are found in the same deposits containing magnesium and aluminum.  First spinels are formed in the presence of both these ellements.  Later when magnesium is exhausted and only aluminum is left the rubies are formed.

 Blue spinel is one of the few singly refractive (SR) transparent blue gems in the market.  If a stone is SR and its refractive index (RI) is between 1.70 and 1.75, it is most likely natural or synthetic spinel.  These are virtually the only identification options for transparent blue SR stones within that RI range.  Gahnite and gahnospinel (other members of the spinel group) have higher refractive indices.

Sources

The first and foremost mine to produce this incredible gemstone is located in Myanmar (Burma) and it continues to offer fine gems to the present time.  Beautiful blue and violet stones of good quality are procured from the second major producer Sri Lanka.  Black colored stones are mined in Thailand at Bo Ploi, Kanchanabur and Madagascar.  It is also found in Pamir Mountains of Tajikistan, Ontario in Canada and New Jersey and New York in United States.  Other countries are Afghanistan, Pakistan, Australia, Italy, Brazil, Sweden, Turkey, Russia, Vietnam and Tanzania.

However, similar to ruby and sapphire, out of all of these sources, only two locations matter to the gem buyer when it comes to value - Mogok for red spinel, Sri Lanka (Ceylon) for cobalt blue.

Color

In the gemstone market, different colors are designated by specific names.  While usually noted for its crimson red hues, spinel color hues are actually far more diverse than just red.
    Ruby spinel -- ruby-red variety of spinel
    Balas ruby -- pink to pale red variety of spinel
    Rubicelle -- yellow to orange variety of spinel
    Flame spinel -- bright orange variety of spinel
    Almandine spinel -- violet variety of spinel
    Blue spinel -- light to dark blue variety of spinel
    Sapphire spinel -- false name describing blue spinel
    Cobalt spinel -- blue spinel colored by cobalt, results in intense, vibrant blue
    'Fancy' spinel -- shades of mauve, violet, purple, blue-green
    Pleonast -- black variety of spinel
    Picotite -- brown variety of spinel
    Gahnite or Gahnospinel -- greenish or bluish, zinc-rich variety of spinel

Color is the most important factor in determining the value of a spinel.  While color preferences are always subjective, the ideal spinel colors display intensity and richness without appearing overcast by black or brown overtones.

There are two main types of natural blue spinel: a common, grayish blue type that is colored by iron; and a rare, vibrant blue type that is colored by a combination of cobalt and iron (typically called "cobalt" spinel).

Colored by iron, and sometimes cobalt, blue spinel is occasionally confused with blue sapphire.  African blue spinel often has the appearance of Montana blue sapphire.

Sri Lanka sometimes produces blue spinels that are colored by cobalt.  Such "cobalt blue" spinels are highly prized by collectors.  The best pieces are an intense blue unique in the world of gems.  The value of these intense cobalt blue spinels can sometimes exceed the finest red spinels.  Blue spinel colored by cobalt is one of the delights of the gem kingdom.

For red spinel, the finest colors tend to be similar to ruby, i.e. a rich, intense red similar to that of a red traffic signal.  Red color appears due to the presence of chromium in its chemical composition.  However, spinel tends to be a bit more of a brick red than ruby (which is slightly more purplish).  Like all gems, the most-highly sought are those whose color is intense, while being not too light or dark.  Prices decline as the color diminishes into either light pinks or "garnety" reds.  Red spinel may be the poor cousin of ruby, but its pinker color and other qualities make it attractive in its own right.

Orange spinels (aka 'Flame' spinels) can also be magnificent.  Look for stones that are a rich orange without too many blackish overtones.

In addition to red, pink, orange and blue, spinel is found in a myriad of other colors.  These are generally termed "fancy" spinels, and occur most often in shades of mauve, violet, purple and blue-green.

The following colors are listed in order of descending cost

Cobalt Blue spinel
Cobalt blue spinel is occasionally unearthed in Sri Lanka.  This precious spinel is highly prized by collectors.  They possess an intense and vibrant blue color that's unlike any other.  The price of cobalt blue spinel can exceed that of the finest red spinel.

Ruby spinel
The color of a perfect red spinel should match that of a fine Mogok ruby: an intense bright crimson that appears neither too light nor too dark.  Their ruby-like appearance is further enhanced by spinel's sparkling luster.

Orange spinel
Sometimes called a "flame" spinel, the orange spinel is extremely beautiful when the color is richly saturated.  At a price range that falls between pink and red spinel, they make an attractive alternative to padparadscha sapphires.  Look for rich orange color without black overtones.

Pink spinel
The boundaries that separate pink and red colors are often difficult for the novice-eye to judge.  But when clearly identified as within the "pink zone," bright, highly clean, beautiful specimens can be purchased at a good price.

Fancy spinel
This spinel color category includes violet, purple, blue-green, and green-violet being the most expensive and green the least.  Colors display all the breadth and depth of a fancy sapphire, at a fraction of the cost.

Clarity

The GIA divides all colored gems into three categories for the purpose of clarity grading, based on the stone's tendency to exhibit inclusions.  The scale is ordered as follows:
TYPE I: Virtually inclusion-free
TYPE II: Usually slightly included
TYPE III: Almost always included
Spinel is a Type II colored gemstone.  Usually slightly included, the spinel falls just short of being thought of as a habitually flawless gem.  Although the ruby and red spinel share the same broad Type II category, the red spinel is habitually cleaner than her famous and more expensive cousin.  However, the very finest reds are so rare that some clarity defect is almost always present (usually fractures).  Included crystals are quite common in spinel.  Many stones display natural iron-oxide stains in their fractures.

This bright colored stone possesses vitreous luster and occurs in massive forms.  It is found in transparent to semi translucent to opaque state.  Transparent stones are usually clean and allow the light to pass through it easily.  Eye clean or crystal clear gems are also available.  Included crystals are quite common in opaque stones.  Fractures are present in translucent gemstones but are not clearly visible.

Often cleaner than ruby, spinel may have some clarity fractures present.  Spinel should essentially be "crystal clear" - allowing a free, unhindered, flow of light throughout its body.  A few of nature's imperfections are to be expected, but they should not diminish the overall appearance.

Cut

Spinel is often cushion cut because its octahedral nature makes the cushion a cost effective cutting design.  The beauty of this stone is enhanced in cushion cut.  In this cut the cutter saves on worthy carat weight.  Round, oval and emerald cut are preferred as a second choice.

Occasionally, perfect octahedral crystals are set into jewelry in their original uncut state - referred to by the Burmese as "nat thwe" or "spirit polished." This "nat thwe" spinel though will sometimes be lightly polished.

Carat Weight

Red and blue colored spinel gemstones more than five carat in weight are rare and highly valuable.  For finger rings and stud earrings, the intense red transparent eye clean gemstone can be procured having the carat weight between 1 and 2.5.  Weight beyond 2.5 ctw would be difficult to obtain.  Similarly, stones of small size are more easily available and can be used for making attractive necklaces with matching earrings, rings, and bangles.  The carat weight of all the stones put together would go up to 25 carats.  It is better to have smaller size stones in the case of bright red and blue colors.

However, other colors are available in all sizes and weights.  For example -- pink colored spinel in different shades as rough is available below 10ctw.  Similarly other colors as well can be procured easily up to the 20ctw as rough.  After the initial gemstone processing, stones weighing between 4-6ctw are created.  With these stones jewelry pieces can be made in attractive designs.

Spinel carat weight impacts per carat prices.  As with most gems, as the carat weight increases, so does the per-carat price.  Because fewer large spinels can be found on the open market, carat prices rise dramatically as carat weights increase.  Spinel pricing suffers from the same "non-linear-scale of increments" as do other precious gems.  This is especially so when dealing with larger, better quality, spinel.

Although large clean spinel is generally not rare, gems on the market are sold mainly in smaller sizes -- less than 5 carats.  Therefore a 7 Carat+ top color quality spinel is indeed rare and highly valuable.

Synthetic spinel

Synthetic spinel has been produced by the Verneuil process since about 1909.  It is made in a variety of colors, some of which are not found in nature.  Spinel has also been grown in Russia by the flux process in red and cobalt-blue colors.

Many people are still unaware of the existence this amazing stone.  They believe that spinel is the name given to the synthetic red colored stone.  Thus, they have to know that this is a semi-precious gemstone occurring naturally and not a man made stone.

The most common method of producing synthetic spinel is by flame-fusion, but flux-grown synthetic spinels may also be seen.  Flame-fusion synthetic blue spinels are usually paler than flux-grown synthetics, which can display the vibrant blues of natural cobalt spinels.

Both flux-grown and flame-fusion synthetic blue spinels show strong absorption bands between 535 and 550 nm, 560 and 590 nm, and 615 and 635 nm.  They also show weak absorption at 430 nm that extends into the UV.  In natural cobalt spinel, the cobalt absorption bands are in similar positions, but a little broader and more diffuse.

Prices

Red spinel has always resided in the shadow of the ruby, with the result that prices are just a fraction of what the equivalent ruby would cost.  Prices of intense cobalt-blue spinels can rival, or even exceed, those for the finest reds.  Because synthetic spinels are often used for imitation birthstone rings, many people think "synthetic" when they hear the name "spinel." This is unfortunate, for a fine gem spinel is one of nature's most beautiful and rare treasures.  In fact, the main thing holding back greater recognition for spinel is rarity.

This poor cousin of the ruby may not be as expensive, but is equally treasured by gem dealers and gem collectors due to its brilliant cut, spectacular colors and wonderful durability.  Moreover, when the same bright color, attractive beauty, and marvelous looks can be acquired for almost one-fourth the price then it is definitely wise to buy the semi precious stone instead of the precious stone.

Good red and blue spinels command prices near the top of the secondary market, but are not anywhere near on par with their ruby and sapphire counter parts.  Pink spinels and other pale colors have far less value.

Spinel is certainly an affordable gemstone when the prices are compared with precious stone but when compared with other semi precious stones it is little expensive.  Buyers need to pay higher price to possess one -- especially the red and blue colors.  Moreover, these days due to rarity in occurrence its prices are increasing.  The irony is that this gemstone is rarer than rubies.

The price for this gemstone is dependent on the color, clarity, carat weight and transparency.  Intense and bright colored transparent stones without too many flaws are priced maximum.  Transparent red and blue colors are most in demand thus are costly but blue stones are very rare hence, fetch a huge price.  Other colors are priced moderately.

Spinel carat weight impacts per carat prices.  Although large clean spinel is generally not rare, gems on the market are sold mainly in smaller sizes, less than 5 carats.  Therefore a 7 Carat+ top color quality spinel is indeed rare and highly valuable.

As with most gems, as the carat weight increases, so does the per-carat price.  Because fewer large spinels can be found on the open market, per-carat prices rise dramatically as carat weights increase.  Spinel pricing suffers from the same "non-linear-scale of increments" as do other precious gems.  This is especially so when dealing with larger, better quality, spinel.

Our thanks to the following organizations for much of the information
Gemological Institute of America
Illustrated Dictionary of Jewelry
Professional Jeweler
Colored Stone