Sardonyx is an agate whose banding is straight and parallel. Much like agate, it is dyed to enhance or change its colors. Dyeing agate was an art practiced by the Romans from early on, but it reached perfection in the 1820s in Oberstein, Germany.

Sardonyx is August's birthstone and makes a great gift for anyone born in this month.

Used as a stone of strength and protection since ancient times, sardonyx is associated with courage, happiness and clear communication. It brings lasting happiness and stability to marriage and partnerships. The spiritual values of red and white-banded and red bullseye sardonyx make these stones particularly powerful. In fact, they are said to allow one to project such an incredible charisma that many people suggest the stone be used with care to avoid overwhelming others. Wear them, they say, when you want extra power in a particular circumstance.

Much of the black and white-banded sardonyx's power comes from its association with a particular body type--slender, quick-moving people who are intellectually active. If you're clever, versatile, highly verbal and have an optimistic disposition, those traits may be heightened when you wear black and white-banded sardonyx. Or, you can wear it to help you control one of those traits if it's working against you. Some believe that placing sardonyx at each corner of a house will protect against evil.