Onyx is a beautiful stone that is commonly used in jewelry and decorative pieces. It is a type of chalcedony that has bands of varying colors, most commonly black and white. Onyxes, therefore, refer to multiple pieces of onyx. Synonyms for onyxes include black agate, black chalcedony, and black quartz. Each of these stones shares some of the same characteristics and can be used in similar ways, but they also have unique variations that make them distinct from one another. No matter what type of onyx or its synonym you choose to use, it is sure to add a touch of elegance to any design or piece.