The name "Spinel" is derived from the Greek word for "spark", referring to its fiery red color. Transparent red Spinel was sometimes called "Spinel Ruby" as it was confused with actual rubies in the past. Spinel, and most other red gemstones were thought to be "ruby," until the late 1700s, when French mineralogist 'Jean Baptiste Louis Rome de Lisle' concluded that spinel was actually a completely different mineral than ruby. Within Great Britain's Crown Jewels are the "Black Prince's Ruby" and "Timur Ruby" which are actually transparent red Spinel.
Originally mined along the Oxus river in north-eastern Afghanistan, these early "Badakhshan" Spinels (aka Balas Ruby) are found in the Crown Jewel collections of Persia (Iran), Russia, and Great Britain. Other historical sources were mined in Burma and Thailand.
Spinel is in the "aluminium oxide" mineral family of corundum. Spinel is found primarily in metamorphic rock, and as a primary mineral in basic rock. Spinel is also found in igneous and carbonate rock. In molten rock or magma, the absence of alkalis (sodium hydroxide or calcium hydroxide) prevents the formation of feldspar. If aluminum oxide is present in the magma, corundum (ruby) will form or the aluminum oxide will combine with magnesium to form Spinel. Ruby and red Spinel derive their coloration from the same Chromium Cr(3+) ion plus trace amounts of iron, manganese, and zinc. This is why spinel and ruby are often found imbedded in the same matrix.
.The crystal structure of spinel is isometric, and its crystal habit is octahedral or twinned octahedral (macles) and to a lesser extent, cubic or dodecahedral.
Spinel has a hardness of 8.0 on the Mohs scale. The Toughness of Spinel is Good. Spinel has a low refractive index and is described as transparent to opaque with a vitreous to dull luster. Spinel has a refractive index of 1.712.
Chemical composition: MgAl2O4
Spinel Mining
The highest quality transparent blood-red "ruby spinel" and hot-pink spinel has come from the Pein Pyit (Painpyit) mine, Bawpadan mine, Inn Gaung Pyant mine, and Pingutaung mine in Mogok, Upper Burma (Myanmar) although these sources are rapidly being depleted. Other significant sources are located in the Mong Hsu stone tract, Myanmar and in Sri Lanka. Due to its high weather resistance, spinel is principally found as crystal pebbles in secondary placer deposits (Myanmar: below, left and Sri Lanka: below, right). Although several times more rare than ruby, fine Burmese spinel is much less expensive.
Yellow spinel is called "Rubicelle" and violet colored spinel is called "Almandine." Spinel occurs in cherry-red (Gemmy), orange, hot pink, mauve, blue, dark green (Gahnite), brown, and black.
The spinel series of minerals melt congruently and recrystallize instantly on cooling making it easy to synthesize. Like corundum (ruby and sapphire), spinel is synthesized by the Verneuil, or "flame-fusion" method by melting aluminum oxide and allowing it to re-crystallize. Many synthetic gemstones such as synthetic aquamarine, peridot, ruby, and sapphire are spinel. The color of synthetic spinel is controlled using chemical additives.
Modern methods of synthesizing corundum, such as the Czochralski Pulled-Crystal, Flux-Grown, and Hydrothermal methods, produce more realistic imitations of ruby and sapphire. These synthetics are identified by their characteristic inclusions.
Natural spinel, like garnet, is one of the few stones that is not normally enhanced or heat treated.
Referance Credits & Suggestions for Further Study
1. Ted Themelis, Mogok: Valley of Rubies & Sapphires 
A & T Publishing, Los Angeles
2. Field Gemology Ruby, Emerald and Spinel Mining in Central Asia . www.fieldgemology.com
3. International Colored Gemstone Association Ruby, Sapphire, and Spinel . www.gemstone.org
4. Judith Crowe, The Jeweler's Directory of Gemstones . DK Publishing.
5. Cally Hall, Gemstones . Simon & Schuster.
6. Walter Schumann, Gemstones of the World . NAG Press; 2Rev Ed edition
