RUBY

Beautiful 4.04 ct. natural Burma ruby and half moon cut diamond ring

Variety:  Ruby
​Species:  Corundum
​​Mohs Hardness:  9 out of 10
Color:  Red.  (Can be light pink to orangy red to strongly purplish red, but red must be the dominant color.)
RI:  1.762 to 1.770 (+0.009 / -0.005)
Birefringence:  0.008 to 0.010
SR/DR/AGG:  DR
Clarity Type:  Type II
Optic Character:  Uniaxial negative
Pleochroism:  Orangy red & slightly purplish red
Spectrum:  Fine lines at 659nm, 668nm, 693nm.  Broad absorption at 500nm to 610nm.
Fluorescence:  Weak to strong red under LW & SW, with best reaction under SW.  Slightly weaker than synthetic ruby.  Heat treated rubies may show chalky fluorescence.
SG:  4.00 (+0.10 / -0.05)
Routine Treatments:  Heating
Additional Enhancements:  Fracture filling, dyeing, diffusion

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Ruby Facts

Photo courtesy of Encyclopedia of Crystal

Rubies, along with emeralds and sapphires, are considered one of the “Top 3” precious gems and often command the highest prices per carat in fine qualities.
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Over 95% of rubies are heat treated to improve their color.  Natural, untreated rubies are more rare, and more valuable, than treated rubies of the same quality.

Ruby is a 9 out of 10 on the Mohs Scale of Hardness, second only to diamond.  Their resistance to scratching, in addition to their beauty, is another reason why they’re so popular in jewelry.​
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​The most valuable rubies have been mined in Burma, the Himalayas & northern Vietnam.  These rubies typically formed within marble.  They have higher chromium content, which is responsible for their intense red color.  The chromium also causes a bright, fire engine red glow when exposed to UV light.​​

Rubies mined in areas such as Thailand and Cambodia tend to be darker in tone, but can also be very valuable.  These basalt-hosted rubies were brought to the earth’s surface by extreme volcanic eruptions.  They have higher iron content, which prevents any fluorescence when exposed to UV light.​

Ruby is a July birthstone and is the 15th & 40th wedding anniversary gemstone.
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SYNTHETIC RUBIES

Star Ruby

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Semi- transparent  to opaque, usually with a 6-rayed star
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Parallel rutile needles intersecting at 60° create a phenomena called "asterism", often amplified by cabochon cutting styles
 
Natural star rubies are usually double cabbed (rounded base) while synthetic star rubies usually have a flat base
 
Synthetic star rubies will usually have curved color banding

Ruby Gallery

​All photos courtesy of Scott Papper, GIA GG, AJP, CMA (NAJA)

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