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Ruby is the most valuable variety of the corundum mineral species, which also includes sapphire.

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Fine Mogok Ruby

This fine 2.58-ct. ruby is from Myanmar’s classic Mogok deposit.

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Ruby’s extraordinary red color is caused by traces of chromium.

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Mixed Cut

Like many fine rubies, this example is fashioned as a mixed cut.

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Calcite Matrix

These exceptional ruby crystals on calcite are from Mogok, Myanmar.

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Origin In Marble

The snow white calcite matrix hints at the ruby crystal’s origin in marble.

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Ruby Crystal

The characteristic form of this ruby crystal allows it to be recognized.

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About Ruby

Rubies can command the highest per-carat price of any colored stone. This makes ruby one of the most important gems in the colored stone market. In its purest form, the mineral corundum is colorless. Trace elements that become part of the mineral’s crystal structure cause variations in its color. Chromium is the trace element that causes ruby’s red color.

Ruby Description Ruby History and Lore Ruby Journey

Birthstones & Anniversaries

Ruby is the birthstone for July and the gem for the 15th and 40th anniversaries.


In Sanskrit, ruby is ratnaraj, meaning the king of gems.


Myanmar’s legendary valley of rubies; the source of many of the world’s most fabulous gems.

$32.4 million

On May 12, 2015, a 25.59-carat ruby ring sold for $1,266,901 per carat, setting a new record at auction for a colored gemstone.


  • Mineral: Corundum
  • Chemical composition: Al2O3
  • Color: Red
  • Refractive index: 1.762 to 1.770
  • Birefringence: 0.008 to 0.010
  • Specific gravity: 4.00 (+/- 0.05)
  • Mohs Hardness: 9

Where It's Found



There are a number of processes used to alter the color, apparent clarity, or improve the durability of gems.

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Some gemstones have synthetic counterparts that have essentially the same chemical, physical, and optical properties, but are grown by man in a laboratory.

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Any gem can be imitated—sometimes by manmade materials or by natural materials chosen by man to impersonate a particular gem.

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Why We Love This Gemstone

Intense Red Glow

Fine ruby glows with intense red in sunlight thanks to red fluorescence, which intensifies its red color.

First laser

The first laser was created in1960 using the red fluorescence light emitted by ruby.


Chromium causes ruby's red. Gemologists consider it the "rock star" of trace elements.

Quality Factors

The prices of fine-quality rubies have been breaking auction records.


quality factors

Color is the most significant factor affecting a ruby’s value: Fine gems are a pure, vibrant red to slightly purplish red.


quality factors

If a ruby's inclusions affect its transparency or brilliance they reduce the gem’s value significantly.


quality factors

Rubies are commonly fashioned as mixed cuts, which have brilliant-cut crowns and step-cut pavilions.

Carat Weight

quality factors

Fine-quality rubies over one carat are very rare and price goes up significantly as size increases.

Ruby Quality Factors: The Comprehensive Guide


Explore sources, gemological research, and the role of gems in history.

Ruby and Sapphire Production and Distribution: A Quarter Century of Change

Russell Shor and Robert Weldon , Jan 1, 2009 Read Article

Identification and Durability of Lead Glass–Filled Rubies

Shane F. McClure, Christopher P. Smith, Wuyi Wang, and Matthew Hall , Apr 28, 2006 Read Article

Rubies and Sapphires from Winza, Central Tanzania

Dietmar Schwarz et al. , Dec 1, 2008 Read Article

Beryllium Diffusion of Ruby and Sapphire

John L. Emmett, Kenneth Scarratt, Shane F. McClure, Thomas Moses, Troy R. Douthit, Richard Hughes, Steven Novak, James E. Shigley,WuyiWang, Owen Bordelon, and Robert E. Kane , Jun 1, 2003 Read Article