A translucent chalcedony usually consisting of straight, parallel bands and coloured black and white in alternating layers (14th century). Onyx is said to have been one of the stones used in the breastplate of the ancient high priest. For hundreds of years, it was carved to produce cameos as the contrast between the different coloured layers heightened the relief. It has been used to alleviate grief, promote self-control and wise decision making and bring happiness and good fortune. It is considered to be useful in the treatment of heart trouble, ear/hearing problems, watery eyes, hair problems and disorders related to bone marrow. It is thought to relieve stress by enhancing self-control and inspiring serenity. Onyx is the zodiac gemstone for Leo (23 July to 22 August).