BIRTHSTONES

Western Tradition
The various cultures which merged into the tradition of "the West"
had many choices of birthstones. Then early in the 19th century, a
council of jewelers got together to standardize a tradition, taking into
account, for instance, what gems were in steady supply at the time.
[Supplies changed, for example, Imperial Topaz became rare and expensive; then an unforeseeable treatment was discovered to turn cheap white Topaz blue, thus the "Birthstone" is changing from golden to blue] I'll list first the standardized Birthstones, and then [later] more ancient traditionals, in the spirit of encouraging you to exercise your free will with a wider pallete of choices. IE: Birthstones are not "set in stone", so if you don't like Peridot, feel as free to redesignate your own Birthstone, as Julius and Augustus Caesar felt free to create new months.

January: Garnet

February: Amethyst

March: Aquamarine , Bloodstone

April: Diamond

May: Emerald

June: Pearl, Alexandrite

July: Ruby

August: Peridot

September: Blue Sapphire

October: Opal, Pink Tourmaline

November: Topaz, [Golden or Blue]

December: Blue Zircon, Turquoise