Cyber Astro.com: Find an astrological sign, which is associated with Astrology Gemstones the constellation www.cyberastro.com. Under the tropical zodiac, Aquarius is occupied by the Sun from January 20 to February 18. The red variety of the mineral corundum, in its finest quality the most valuable of Astrology Gemstones. Only medium to dark tones of red to slightly violet-red or very slightly orange-red are called ruby; light reds, purples, and other colors are properly called sapphires. In its pure form the mineral corundum, with composition is colorless. The rich red of fine-quality ruby is the result of the presence of a minute amount of chromic oxide. The chromium presence permits rubies to be used for lasers producing red light.

The finest ruby is the transparent type with a medium tone and a high intensity of slightly violet-red, which has been likened to the color of pigeon's blood. Star rubies do not command comparable prices, but they, too, are in great demand. The ruby was among the first of the gemstones to be duplicated synthetically and the first to be used extensively in jewelry. See also Gem.