Onyx

Onyx is the mystical birthstone for the month of December. It is usually black and has a fine texture; however some onyx stones also display white bands or ribbons against a black or brown background – this variety is known as sardonyx.
The name comes from the Greek word onyx which means “fingernail”. According to a legend one day while Venus was sleeping Eros cut off her fingernails and left the clippings scattered on the ground. Because no part of a heavenly body can die, the gods turned them into stone which later became known as onyx. This stone is believed to bear many mystical powers.