Onyx is the Mystical birthstone for the month of December. It is also the birth stone for the Zodiac sign of Leo. Ancient legends says that one day while Venus was sleeping, Eros cut her fingernails and scattered them on Earth. Because no part of a heavenly body can die, the gods turned them into stone which later became known as Onyx. Originally, almost all colors of Chalcedony from white to dark brown and black were called Onyx.  Today Onyx is often prefaced with the word with black to distinguish it from other varieties of Onyx that come in white, reddish brown, brown and banded, known as Sardonyx. In contemporary stone lore, it is rumored Onyx decreases sexual desire and aids in controlling bad habits.