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Encyclopedia > Rubies
For other uses, see Ruby (disambiguation).
Title
Enlarge
Ruby crystal before faceting, length 0.8 inches (2 cm).
General
Category Mineral
Chemical formula aluminium oxide, Al2O3
Identification
Colour Red, may be brownish
Crystal habit Varies with locality. Terminated tabular hexagonal prisms.
Crystal system Trigonal
Cleavage No true cleavage
Fracture Uneven or conchoidal
Mohs Scale hardness 9.0
Luster Vitreous
Refractive index ~1.77
Pleochroism  ?
Streak  ?
Specific gravity 4.0
Fusibility  ?
Solubility  ?
Major varieties
Corundum Ruby when uncontaminated with chromium

Ruby is a red gemstone, a variety of the mineral corundum in which the color is caused mainly by chromium. Its name originates from ruber, Latin for red. Natural rubies are exceptionally rare, though artificial ones can be manufactured which are comparatively inexpensive.


Rubies are mined in Africa, Asia and Australia. They are most often found in Myanmar, Sri Lanka and Thailand, though they have also been found in Montana and South Carolina. Sometimes spinels are found along with rubies in the same geological formations and are mistaken for the more valuable gem. However, fine red spinels may approach the average ruby in value.


Rubies have a hardness of 9 on the Mohs scale of mineral hardness, and among the natural gems are only surpassed by diamonds in hardness. Other varieties of corundum are called sapphires.

Enlarge
A cut ruby

Ruby gemstones are valued according to several characteristics including size, colour, clarity and cut. All natural rubies have imperfections in them. On the other hand, artificial rubies may have no imperfections. 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)—then it is suspected of being artificially made and its status as a priceless gem is therefore not assured. Some manufactured rubies have dopants added to them so that they can be identified as artificial, but most require gemmological testing to determine their origin.


A synthetic ruby crystal was used to create the first laser.


Ruby is the birthstone associated with July.


The world's biggest star ruby is the Rajaratna Ruby, which weighs 2,475 carats. The world's biggest double-star ruby (with a 12-pointed star) is the Neelanjali Ruby, weighing 1,370 carats and they both currently belong to Mr. G. Vidyaraj from Bangalore in India.


See also


  Results from FactBites:
 
CSS3 Ruby Module (3826 words)
"Ruby" is the commonly used name for a run of text that appears in the immediate vicinity of another run of text, referred to as the "base", and serves as an annotation or a pronunciation guide associated with that run of text.
The ruby structure and the XHTML markup to represent it is described in the Ruby Annotation [RUBY].
If the width of the ruby text is smaller than that of the base, then the ruby text contents are evenly distributed across the width of the base, with the first and last ruby text glyphs lining up with the corresponding first and last base glyphs.
Neelanjali Ruby - encyclopedia article about Neelanjali Ruby. (409 words)
The Neelanjali Ruby is the world's largest star ruby with a 12 point asterism, which is commonly denoted as a double-star ruby.
The ruby belongs to G. Vidyaraj and is reported to be in Bangalore, India.
Ruby is a red gemstone, a variety of the mineral corundum (aluminium oxide) in which the color is caused mainly by chromium.
  More results at FactBites »


 

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