Ruby

Natural Faceted Gems

Ruby is the red gem variety of corundum, an aluminium oxide mineral. Chromium in the crystal structure produces colors from orangy red to purplish red; its Mohs hardness of 9 and lack of true cleavage make it well suited to jewelry.

Identity

Material or variety: Ruby
Scientific or material identity: Corundum
Classification: Natural mineral or mineral variety
Composition or formula: Al₂O₃
Crystal system or structure: Trigonal
Geological or manufacturing origin: Can form in more than one geological environment, or combines several materials.
Mohs hardness: 9
Specific gravity: 3.95 to 4.10

Origins

Madagascar · Mozambique · Myanmar · Sri Lanka · Thailand

Appearance & optical properties

saturated crimson corundum.

History & discovery

The name comes from the Latin ruber, meaning “red.” Pliny described rubies in the first century CE, while Myanmar has supplied them since at least the sixth century. Some celebrated historic “rubies,” including the Black Prince’s Ruby, were later identified as red spinel.

Uses & care

Common uses: Ruby is faceted or cut as a cabochon for rings and other jewelry. Stones with oriented rutile silk may be fashioned as cabochons to show a moving star.
Handling and cleaning: Clean ruby with warm soapy water. Corundum is tough and stable in normal wear, but stones with surface-reaching fractures or uncertain treatments should avoid steam, ultrasonic cleaning, acids, and hard knocks.

Jewellery

7 pieces of Ruby jewellery. Learners earn each one in DigMyGem by learning words; until then it shows as a silhouette.

DeLong Star Ruby
Ring
A 100.32-carat star ruby that shows a six rayed star in sunlight and was famously stolen from a museum in 1964.
Photo: Vicpeters, CC BY 4.0, via Wikimedia Commons
Sunrise Ruby
Ring
A 25.59-carat Burmese pigeon-blood ruby, mounted by Cartier between two large diamonds. It set a world auction record at Sotheby's Geneva in 2015 when it sold for US$30.42 million.
Rosser Reeves Ruby
Jewel
At 138.7 carats this Sri Lankan star ruby is one of the largest and finest in the world, famed for its sharp six-ray star. The advertising mogul Rosser Reeves carried it as a lucky stone before donating it to the Smithsonian in 1965.
Photo: thisisbossi from Washington, DC, USA, CC BY-SA 2.0, via Wikimedia Commons
Estrela de Fura
Jewel
Estrela de Fura is a ruby of about 55 carats cut from a 101-carat crystal found in Mozambique. It is one of the largest gem-quality rubies known.
Neelanjali Ruby
Jewel
The Neelanjali Ruby weighs about 1,370 carats and is the largest double-star ruby in the world. It comes from India.
Liberty Bell Ruby
Jewel
The Liberty Bell Ruby was carved from the largest mined ruby into a small model of the Liberty Bell. It is set with fifty diamonds.
Prince of Burma
Jewel
The Prince of Burma is a gem-quality ruby of about 950 carats found at Mogok in Myanmar in 1996. It is one of the largest uncut rubies in the world.