Gemstones have been assigned to each of the 12 months of the year. The practice of wearing gemstones is believed to relate back to the 12 stones on the breastplate of Aaron, brother of Moses, and is thought to bring god fortune.

This list comes from Julia and Derek Parker's Astrology.

Aries: Diamond
Taurus: Emerald
Gemini: Agate
Cancer: Pearl
Leo: Ruby
Virgo: Sardonyx
Libra: Sapphire
Scorpio: Opal
Sagittarius: Topaz
Capricorn: Turquoise
Aquarius: Aquamarine
Pisces: Moonstone

Do the months also have their own gemstones seperate from the actual signs themselves? I was under the impression that february birthdays were Amethyst. So does this mean that because I was born in February and I'm also an Aquarius that I have two astrological birthstones associated with myself? Was I wrong in thinking that each month had their own gemstone and that really its only associated with the signs themselves?