Ruby

Madagascar
6.29 carats
© gemselect.com

Ruby is a pink to blood-red coloured gem variety of the mineral Corundum. The name comes from the Latin word "ruber" - red.

The red colour can vary within each individual deposit, therefore the determination of the source from the colour is not possible. The red colour is caused by chromium, and in case of brownish tones due to presence of iron.

The rough stone has dull and greasy lustre.

Inclusions are common and often indicate that the stone is natural.

130 photos

Ruby Gemstones by Colour

This table shows the variety of hues this gemstone can be found in. Click on a photo for more information.

Ruby Gemstones by Size

This table shows distribution of Ruby gemstone sizes that are listed on this site. This can give a good indication as to the general availability of this gemstone in different sizes.

Contributed photos

Lightest:0.12 cts

Heaviest:100.32 cts

Average:4.89 cts

Total photos:120

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Significant stones

Eminent Star6,465 cts

Ecce Homo Star Ruby2,890 cts

Edwardes Ruby167 cts

Rosser Reeves Star Ruby139 cts

Anne of Brittany's105 cts

0.12ct to 10.14ct10.14ct to 20.16ct20.16ct to 30.18ct30.18ct to 40.20ct40.20ct to 50.22ct50.22ct to 60.24ct60.24ct to 70.26ct70.26ct to 80.28ct80.28ct to 90.30ct90.30ct to 100.32ct

General Information

A variety or type of:

Corundum

Varieties/Types:

Flux-Grown Ruby - A synthetic ruby grown from alumina dissolved in a molten flux.

Geneva Ruby - Earliest synthetic rubies (circa 1885) created in Geneva.

Star Ruby - A chatoyant ruby showing asterism.

Verneuil Ruby - A synthetic ruby created using the flame fusion process.

Chemical Formula

Michael O�Donoghue, Gems, Sixth Edition (2006)

Significant stones

Name	Weight	Country of Origin	Current Owner
Eminent Star	6,465.00 cts	India
Ecce Homo Star Ruby	2,890.00 cts	Mozambique
Edwardes Ruby	167.00 cts
Rosser Reeves Star Ruby	138.70 cts	Sri Lanka
Anne of Brittany's	105.00 cts
DeLong Star Ruby	100.32 cts	Myanmar	American Museum of Natural History
De Long Star Ruby	100.32 cts	Myanmar
Edith Haggin de Long Star Ruby	100.32 cts	Myanmar

Click here to view all significant Ruby gemstones

Ruby Treatments

Heat-treatment may create a superficial chalky-blue reaction. May be dyed (especially cabochons): color concentration in cracks. Acetone test.
Diffusion: may show orangy color concentration/rim under surface. May show blue haloes/spots (internal diffusion). May be surface diffused (chromium): rare. Glass filling: rounded and flattened gas bubbles, glassy residues. Reflecting light: filled cracks may show a distinct surface lustre. Lead-glass (and some other high refractive glasses) may be revealed by bluish to orangy flashes seen when looking parallel to filled cracks, using dark-field or fiber-optic light. Some glass-filled rubies may not show colored flashes nor show obvious gas bubbles. Sensitive to solvents - Blue Chart Gem Identification, Herve Nicolas Lazzarelli, 2010, p. 2
Lattice diffusion with beryllium enhances the colour giving orangy-red or red face-up colour. Fracture-filling with high-lead-content glass.Exposure to chemicals (even some household cleaners) can damage the filler material and make fracture more visible. - GIA, 2018

Ruby Simulants

Imitation rubies are also marketed. Red spinels, red garnets, and colored glass have been falsely claimed to be rubies. Imitations go back to Roman times and already in the 17th century techniques were developed to color foil red�by burning scarlet wool in the bottom part of the furnace�which was then placed under the imitation stone.

Synthetic Ruby

In 1837 Gaudin made the first synthetic rubies by fusing potash alum at a high temperature with a little chromium as a pigment. In 1847 Ebelmen made white sapphire by fusing alumina in boric acid. In 1877 Frenic and Freil made crystal corundum from which small stones could be cut. Frimy and Auguste Verneuil manufactured artificial ruby by fusing BaF2 and Al2O3 with a little Chromium at red heat. In 1903 Verneuil announced he could produce synthetic rubies on a commercial scale using this flame fusion process. By 1910, Verneuil's laboratory had expanded into a 30 furnace production facility, with annual gemstone production having reached 1,000 kg (2,205 lb) in 1907.

Other processes in which synthetic rubies can be produced are through the Czochralski's Pulling process, flux process, and the hydrothermal process. Most synthetic rubies originate from flame fusion, due to the low costs involved. Synthetic rubies may have no imperfections visible to the naked eye but magnification may reveal curves, striae and gas bubbles. The fewer the number and the less obvious the imperfections, the more valuable the ruby is; unless there are no imperfections (i.e., a "perfect" ruby), in which case it will be suspected of being artificial. Dopants are added to some manufactured rubies so they can be identified as synthetic, but most need gemological testing to determine their origin.
Synthetic rubies are used for watches and bearings, formerly the most important technical application for natural stones. - Gemstones of the world, Walter Schumann, 2001, p 82

Physical Properties of Ruby

Mohs Hardness

Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)