In jewellery design as in fashion, colours look crisper against a background of black, and black and white always looks right. In fine jewellery, the black backdrop is often supplied by onyx, a black chalcedony quartz with a fine texture. Some onyx also displays white bands or ribbons against a black background. If the layers are even, this type of onyx can be carved into cameos.
Onyx was very popular with the ancient Greeks and Romans. The name comes from the Greek word 'onyx', which means nail or claw. The story is that one day the frisky Cupid cut the divine fingernails of Venus with an arrowhead while she was sleeping. He left the clippings scattered on the sand and the fates turned them into stone so that no part of the heavenly body would ever perish. True, black isn't normally the colour one associates with fingernails. (Did Venus wear Vamp, perhaps?) But in Greek times, almost all the colours 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 colours only.
Onyx which is reddish brown and white is known as sardonyx. Sardonyx was highly valued in Rome, especially for seals, because it was said never to stick to the wax. The Roman general Publius Cornelius Scipio was known for wearing it a good deal.
Black onyx shines especially well when used as a backdrop for colour play. Its fine texture also makes it ideal for carving, making it a favoured material for today's lapidaries. In the pin by designer Susan Helmich above, a carved piece of onyx with threads of white provides a stunning backdrop for a flash of colour. Onyx was often used as the perfect foil for carved rock crystal or the 'drop dead red' of rubies in art deco designs. It is also popular in marcasite jewellery. So if you would like to add a little black magic to your jewellery design.
Black onyx is the name given to a black translucent form of chalcedony ( pronounced "kal ¬∑ SED ¬∑ nee" ). Chalcedony is a form of silica, therefore it is similar to the quartz family of minerals. The difference between quartz and chalcedony is the crystal formation.
Chalcedony is made up of tiny microscopic crystals, or microcrystalline. Quartz crystal are larger, ranging from clusters of tiny points on a rocks surface, to huge single crystals. Amethyst and citrine are both forms of quartz.
Chalcedony and quartz are both clear colored minerals. Silica is a clear mineral, the different colors we see in the various gemstones come from impurities in the stone. In the case of black onyx, carbon is usually the mineral creating the dark color.
Black onyx is a hard durable gemstone that takes an exceptional polish. Black onyx is also colorfast, therefore it will not fade or change colors.