Here's the list of the twelve birthstones with their corresponding month:
January - Garnet
February - Amethyst
March - Aquamarine/Bloodstone
April - Diamond
May - Emerald
June - Pearl/Alexandrite/Moonstone
July - Ruby
August - Peridot/Spinel
September - Sapphire
October - Tourmaline/Opal
November - Topaz/Citrine
December - Tanzanite/Zircon/Turquoise
What's yours?