Azurite is a carbonate mineral formed in the oxidized portions of copper deposits. Its crystals can take over 145 different forms and its color varies from a beautiful azure blue to a much darker blue-black. Azurite and malachite often occur in the same formations.
Malachite is a shining copper ore with swirling islands of rich green color. Used since ancient Egyptian times as pigment for cosmetics, dyes and paints, malachite's primary use today is still ornamental. Popularized in modern times in 19th century Europe, it was worn as protection against the "evil eye." Much of today's fine malachite is mined in the Congo.
Onyx is a chalcedony quartz with a fine texture and black color. Some onyx also displays white bands or ribbons against a black background. Onyx was popular with the ancient Greeks and Romans. The name comes from the Greek word "onux," which means fingernail. The myth is that Cupid cut the divine fingernails of Venus one day while she was sleeping. He discarded the clippings and the fates turned them to stone so that no part of Venus would ever be lost. In Greek times, almost all colors of chalcedony from fingernail white to dark brown and black were called onyx. Later, the Romans narrowed the term to refer to black and dark brown colors only.