Ruby
Ruby is a
red gemstone, a variety of the
mineral corundum . The color is caused mainly by
chromium. Its name comes from
ruber,
Latin for red. Natural rubies are exceptionally rare, but synthetic rubies can be manufactured fairly cheaply. Other varieties of gem-quality corundum are called
sapphires. It is considered one of the four precious gems together with the
sapphire, the
emerald and the
diamond.
Rubies are mined in
Africa,
Asia,
Australia, and
Greenland. They are most often found in
Myanmar ,
Sri Lanka,
Kenya,
Madagascar, and
Thailand, but they have also been found in the
U.S. states of
Montana,
North Carolina and
South Carolina.
Encyclopedia
| Ruby | Ruby crystal before faceting,
length 0.8 inches . | General | Category | Mineral | Chemical formula | aluminium oxide with chromium, Al2O3Cr | Identification | Color | Red, may be brownish or purplish | Crystal habit | Varies with locality. Terminated tabular hexagonal prisms. | Crystal system | Hexagonal | Cleavage | No true cleavage | Fracture | Uneven or conchoidal | Mohs Scale hardness | 9.0 | Lustre | Vitreous | Refractive index | ~1.762-1.770 | Pleochroism | Orangy Red, Purplish Red | Streak | white | Specific gravity | 4.0 | Fusibility | perfectly | Solubility | ? | Major varieties | Pink sapphire | Caused by a color impurity
and makes the stone
appear pink. | | |
Ruby is a
red gemstone, a variety of the
mineral corundum . The color is caused mainly by
chromium. Its name comes from
ruber,
Latin for red. Natural rubies are exceptionally rare, but synthetic rubies can be manufactured fairly cheaply. Other varieties of gem-quality corundum are called
sapphires. It is considered one of the four precious gems together with the
sapphire, the
emerald and the
diamond.
Rubies are mined in
Africa,
Asia,
Australia, and
Greenland. They are most often found in
Myanmar ,
Sri Lanka,
Kenya,
Madagascar, and
Thailand, but they have also been found in the
U.S. states of
Montana,
North Carolina and
South Carolina. The Mogok Valley in
Myanmar has produced some of the finest rubies but in recent years very few good rubies have been found there. In central Myanmar the area of Mong Hsu also produces rubies. The latest ruby deposit to be found in Myanmar is situated in Nam Ya. In 2002 rubies were found in the Waseges River area of
Kenya. Rubies are being mined at Audilamena in northeastern
Madagascar. Sometimes
spinels are found along with rubies in the same rocks and are mistaken for rubies. However, fine red spinels may approach the average ruby in value.
Rubies have a
hardness of 9.0 on the Mohs scale of mineral hardness. Among the natural gems only
diamond is harder.
Ruby gemstones are valued according to size, color, clarity and cut. All natural rubies have imperfections in them, including color impurities and inclusions of
rutile needles known as "silk". If there is no silk in the stone, that shows that the stone was heated at 3000°C to give the ruby a better color of red. Usually the rough stone is heated before cutting.
Colour, clarity and cut
Rubies come in shades of red, red purple and red orange. A medium toned red or red with slight purple is most desired. Clarity of the stone and inclusions are also taken into account to determined the stones value. A purple or orange stone is called a fancy
sapphire. Burmese rubies have a deep red to slightly purplish red color. Thai rubies are of a brownish color, which is generally less attractive and therefore commands lower prices. Generally, medium to high quality rubies that are transparent are normally
faceted. In comparison those which are translucent and opaque are normally cut into cabochons, emphasizing more on weight rather than the quality of the cut.
Phenomenon
Rubies occasionally show an optical phenomenon called asterism when cut into a cabochon. These are called "star rubies" and can be more valuable than normal rubies because asterism is rare.
They also very rarely show color change and chatoyancy.
Synthetic and imitation rubies
Synthetic rubies have been made since the late 19th century. They have become more common since the work of Auguste Verneuil and the introduction of the
flame fusion process. Other processes in which synthetic rubies can be produced are through the 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 curved 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 , 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 gemmological testing to determine their origin. Imitation rubies have also been present in the gemstone market for sometime. Red spinel, red garnet and even glass have been falsely named as rubies. Trade terms such as
balas ruby for red spinel and
rubellite for red
tourmaline can mislead unsuspecting buyers. Such terms are therefore discouraged from being used by many gemmological associations such as the Gemological Institute of America .
Identifying Synthetic Rubies
Most synthetic rubies can only be identified using at least a 10x magnification
microscope or a
loupe or a lightsource such as a lamp or a penlight.
Flame Fusion
- Show curved growth lines
- May also show included gas bubbles
Pulling
Flux
- Translucent to opaque included crystals or liquids
- Wispy like veils
- Wavy fingerprint-like inclusions
Other than
fluorescence, magnification is the only way to differentiate between a synthetic and a natural ruby
Records
The world's biggest ruby is the Rajaratna Ruby, which weighs 2,475 carats . Because the Rajaranta shows asterism, it is also the largest star ruby. The world's biggest double-star ruby is the Neelanjali Ruby, weighing 1,370 carats . Both rubies belong to G. Vidyaraj from
Bangalore,
India.
A 8.62 ct.
Burmese ruby sold for $425,000 per carat or $3,800,000 on 15 February 2006 at
Christie's in
Switzerland.
Culture and historical/mythical usage
A
synthetic ruby crystal was used to create the first
laser.
According to
Rebbenu Bachya, the word
odem in the verse Exodus 28:17 means "ruby"; it was the stone on the Ephod representing the tribe of Reuben. Modern
Hebrew has taken this meaning.
Ruby is also the most commonly named precious stone in the Bible; an example being Proverbs 31: "
A virtuous wife is worth more than rubies."
Ruby is the
birthstone associated with July.
Ruby symbolizes passionate love.
See also
