Ruby is a type of Corundum which crystalizes in the form of tabular and rhombohedral prismatic crystals. It sometimes exhibits dichroism, displaying crimson-red and orange-red in the same stone. It also, occasionally, displays asterism (a star like luminosity in transmitted light). Some Rubies from Thailand also contain Analcime crystals. The Ruby has been known since before the time of the Bible; it was named from the Latin word meaning "red".
Chemical Composition: Al2O3
"The Ruby.—The Ruby is one of the most precious of gems, when of a good size, free from flaws, and of the true pigeons’-blood colour, being more valuable than a diamond of the same size.The finest rubies come from Burmah, and they are also found in Ceylon and Siam; their colour varies from light pink to the richest carmine. Until modern times the Spinel or Balas Ruby was included with the true Ruby, but they are quite different in their composition, Spinels being softer and not so brilliant, though more varied in colour, ranging from red, orange, green, and blue to violet.
Amongst Oriental nations this stone has ever and still continues to be a great favourite as a Talisman; and throughout India, Burmah, and Ceylon it is considered to guard its wearers from the attacks of enemies, reveal the presence of poison by changing colour, and to attract friends and good fortune.In China and Japan it is also worn to confer long life, health, and happiness. Pliny describes it as the Lychnis, and says the Star Rubies were considered by the Chaldeans to be most powerful in protecting from evil and attracting the favour of those in authority.
Throughout the whole of the Orient the Ruby was believed to possess the power of foretelling danger by a loss of brilliancy and colour, a belief also common throughout Europe as confirmed by Wolfgangus Gabelschoverus, who writing in the year 1600, says, whilst travelling with his wife:
"I observed by the way that a very fine Ruby (which she had given me) lost repeatedly and each time almost completely its splendid colour and assumed a blackish hue."
He goes on to tell that the threatened evil was fulfilled by the loss of his wife, and that after her death the stone regained its colour and brilliancy.Catherine of Aragon is reported to have also possessed a ring set with a ruby that indicated in the same manner the approach of misfortune.
Camillus Leonardus says that the Ruby gave control of the passions, drove out evil thoughts, secured possessions to their rightful owner, reconciled quarrels, brought peace and concord, also preserved bodily strength and health, and that the Balas Ruby (Spinel) possesses the power of averting danger of hail and tempest.It was worn by the subjects of this House whose horoscopes were free from Saturn's afflictions to protect the body from plague, poison, and fevers, and to secure love and friendship, preserve health, vitality, and cheerfulness, against disorders of the liver and spleen, and to drive away evil dreams and spirits.
It was also believed to be a very active and sensitive stone, and if the horoscope had Saturn badly afflicted would afford a ready channel for disappointment, bereavement, and other misfortunes incidental to the influence of this planet when malefic."
-The Book of Talismans, Amulets and Zodiacal Gemsby William Thomas and Kate Pavitt 1922