Spinel
The Black Prince's Ruby. The Timur Ruby. For centuries, spinel, the great imposter, masqueraded as ruby in Europe's crown jewels.
OVERVIEW
About Spinel
Until recently, spinel was an underappreciated gem with little consumer recognition. Increasing demand for ruby alternatives rekindled appreciation for spinel’s rich red color and history. In ancient times, southeast Asia’s mines yielded exceptional large spinel crystals, which became the treasured property of kings and emperors, often passing through many hands as spoils of war.
Birthstones & Anniversaries
Spinel was recently added as an August birthstone, sharing this month with peridot and sardonyx. It has long been mistaken for ruby by emperors and monarchs. Many of the famous “rubies” of history were actually spinels.
Nat Thwe
Spinel crystals are so perfect, in Burma they are said to be nat thwe or “polished by the spirits.”
Black Prince
The famous 14th century Black Prince’s Ruby in the British Imperial Crown is actually a red spinel.
1783
Mineralogist Jean Baptiste Louis Rome de Lisle identifies spinel as a different mineral than ruby.
FACTS
Mineral: spinel
Chemistry: MgAl2O4
Color: red, orange, pink, purple, blue, black
Refractive index: 1.718
Birefringence: none
Specific gravity: 3.60
Mohs Hardness: 8
TREATMENTS
There are a number of processes used to alter the color, apparent clarity, or improve the durability of gems.
SYNTHETICS
Some gemstones have synthetic counterparts that have essentially the same chemical, physical, and optical properties, but are grown by man in a laboratory.
IMITATIONS
Any gem can be imitated—sometimes by manmade materials or by natural materials chosen by man to impersonate a particular gem.
WHY WE LOVE THIS GEMSTONE
1
STUNNING COLOR
Singly refractive and often very transparent, red spinel rivals ruby’s color but it costs much less.
2
AMAZING CHROMIUM
Red spinel is colored by chromium, the same trace element that colors ruby and emerald.
3
BIRTH OF GEMOLOGY
Distinguishing spinel from ruby gave birth to the science of gemology.
Quality Factors
An assessment of the following characteristics determines spinel’s value.
COLOR
The most valued spinel colors are bright red, cobalt blue, and vivid pink and orange. Pale lavender is more affordable
CLARITY
Spinel with no visible inclusions is preferred. The more prominent the inclusions, the less valuable the gem.
CUT
Spinel is most often cut in cushion and oval shapes. When properly proportioned it has excellent brilliance.
CARAT WEIGHT
Fine-color spinel is rare above five carats. Most fine-quality rough is cut to non-standard sizes to save weight.
Spinel Quality Factors: The Comprehensive Guide
RESEARCH
Explore sources, gemological research, and the role of gems in history.
GIA Staff , Oct 6, 2016
Boris Chauviré, Benjamin Rondeau, Emmanuel Fritsch, Phillipe Ressigeac, and Jean-Luc Devidal , Apr 30, 2015
RECOMMENDED READING
Report on Ruby and Spinel in Manya (Northern Burma); Identifica-tion of Spinel and Ruby from Namya
Dr. A. Peretti
The John Sinkankas Spinel Symposium: April 18, 2009
John Sinkankas Memorial Symposium
Terra Spinel: Terra Firma
Vladyslav Y Yavorskyy
