Onyx is often mistakably categorized as an agate, but is actually a type of chalcedony that is formed within gaseous cavities in lava. It is a banded black (or dark brown) and white chalcedony that resembles agate, hence the confusion. 

Black onyx is most often a chemically-treated, dyed gray chalcedony, but it can rarely be found in nature as well.

This mineral has been utilized for jewelry as intaglios and cameos for thousands of years. The term "onyx" comes from the Greek word for fingernail. Historians believe early onyx were tan like a fingernail color, but legend says Cupid used his arrows to give Venus a manicure causing her nails to fall off into a river, becoming onyx. 

Onyx occurs all over the world in countries like Afghanistan, Madagascar, Peru, India and the United States. 

Size: 1.19 x 1 x 3.5 inches

Weight: 3.35 oz.