What is the birthstone for people born in December?

Blue Topaz, Turquoise, or Blue Zircon

The birthstone for the month of December is a blue zircon, which is a gemstone. But when cubic zirconias hit the mass market people became confused between the two so blue topaz or turquoise were added. There are different colors of zircons, but only blue is December.

There are also gems designated for Zodiac signs. December 22 makes you a Capricorn, which is a ruby.

Traditional - ziricon, ruby

Modern - turquoise, blue topaz

Mystical - onyx

Ayurvedic - ruby