Each month has at least one official birthstone, beginning with January, which is garnet, and followed by amethyst for February, aquamarine for March, diamond for April and emerald for the month of May. The birthstone for June is pearl, July is ruby, August is peridot, September is sapphire, October is opal, November is citrine, and December is blue topaz. The official list of modern birthstones was created in 1912, and has only been altered once since, in 2002, when tanzanite became the fourth birthstone to be associated with December.
Several months claim multiple modern birthstones. March, October and November all have secondary birthstones. March's second stone is bloodstone, October's second one is tourmaline and November's second stone is topaz. June has two additional birthstones, which are alexandrite and moonstone. December has the additional three birthstones of tanzanite, zircon and turquoise.
Birthstones have also been linked to the zodiac signs. Capricorn is ruby, Aquarius is garnet, Pisces is amethyst, Aries is bloodstone, Taurus is sapphire, Gemini is agate and Cancer is emerald. Leo is associated with onyx, while Virgo is carnelian, Libra is peridot, Scorpio is beryl and Sagittarius is topaz.
The custom of wearing a birthstone is one that has been documented in a variety of ancient cultures. In addition to modern and zodiac birthstones, there are also distinct Hebrew, Roman, Arabic, Hindu, Polish, Russian and talismanic stones, all associated with different birth months.