history, spinel has been confused with ruby. In part, this
is because spinel is often found in the same deposits. Gem
spinel is a magnesium aluminum oxide, while ruby (corundum)
is an aluminum oxide. In deposits where both ruby and red
spinel are found, spinel is typically more common than ruby.
This is because, when both magnesium and aluminum are present,
spinel grows. Only after the magnesium is exhausted, does
ruby get a chance to crystallize. In addition, both ruby
and red spinel owe their color to the same Cr+3 ion.
is most likely that the famous Mogul
spinels as described in Dr. Balls
article above originated from mines
long-since abandoned along the Amu
Darya (Oxus) river that separates
present-day Tajikistan from Afghanistan.
The locality is just inside Tajikistan,
about 47 km. south of Khorog, on
the edge of the Pyandzeh river valley.
examples of these Badakhshan spinels
can be found in some of the
most famous gem collections
in the world. Perhaps the
largest single grouping is
in the Crown Jewels of Iran
in Teheran. Others can be
found in the British Crown
Jewels in the Tower of London
and the Kremlin in Moscow.
colored by cobalt is one of the delights of the gem kingdom.
Above is a particularly fine example.
Photo: John McLean; Stone: Dr. Richard Bartholomeau
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. 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.
spinels (also known as flame spinels)
can also be magnificent. Look for stones
that are a rich orange without too many
|One of the
finest examples of a Badakhshan spinel is the Black
Princes Ruby, a 170-ct. monster
which is mounted in the front of the Imperial State
Crown of Great Britain. It is on public display at
the Tower of London. Photo: Younghusband, G. and
Davenport, C. (1919) The Crown Jewels of England. London,
Cassell and Co., 84 pp.
Lanka rarely produces blue
spinels colored by cobalt. Such cobalt blue
spinels are highly sought after
by collectors. The best pieces
are an intense blue unique
in the world of gems.
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.
In terms of clarity, spinel is often cleaner than ruby. 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.
Due to the octahedral nature of spinel rough, the most common shape seen is the cushion. Rounds are also seen, as are other shapes, such as the emerald cut.
Red spinel has always resided in the shadow of 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.
spinels of 100 carats or greater are known, top red or
blue stones in
sizes above five carats are rare. Fancy spinels in
sizes up to 20 carats or more are generally available.
Spinel typically occurs as octahedra or twinned octahedra (macles), either well-formed or flattened. Specimens from Burma’s Mogok Stone Tract are often so perfect that they are mounted in jewelry as is. Such stones are termed nat thwe (‘spirit polished’).
name spinel is believed to derive from the Latin word, spina, meaning thorn, perhaps
in allusion to the pointed shape typical of spinel octahedra.
In the past, spinel has been referred to as balas ruby,
a reference to the mines of Badakhshan.
fine spinels come from a handful
of sources. The best red, pink
and orange spinels originate from the
rich gem gravels of Burmas
Mogok Stone Tract. The best blue
and violet spinels are found in
Sri Lanka (Ceylon). Gem spinel
found in Vietnam, the Pamir mountains
of Tajikistan, Tanzania and Madagascar.
Black spinel is mined in Thailand
(at Bo Ploi, Kanchanaburi).
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
nature. Spinel has also
been grown in Russia by the flux
process in red and cobalt-blue
is a comparison of some of the properties of spinel and corundum:
(Ruby & Sapphire)
(0.008) Uniaxial (–)
colorless, red, pink, orange, green, blue, violet, purple.
(except an emerald-green)
(4 & 6 rays), cats eye
(6 & 12 rays)
special care needed
special care needed
none; occasionally oiling, dying
including heat, heat + flux healing, surface-diffusion,
irradiation, oiling, dying, glass-infilling
From this table, one can see how similar
spinel and ruby are. Thus the confusion.
For historical information on Badakhshan
spinels, as well as technical information about spinel:
The Collector Gem Buying Guides
In addition to the above, please visit the Learning
Vault at Palagems.com for many additional articles on gems, minerals and mining.