These classic black onyx earrings could be found here.
Onyx is a gemstone whose description can have several connotations. Its most accepted gemstone definition describes a solid black Chaledony, or a banded or layered black and white Chalcedony. The term Onyx is occasionally used to described any engraved stone with a solid color base, or it may describe any banded gemstone with parallel banding. In its solid black form, Onyx is the most traditional black gemstone.
Chalcedony is the form of Quartz that is compact and microcrystalline. It occurs in many different forms, colors, and patterns, and many varieties have been used as gemstones since antiquity. In the gemstone trade, the term Chalcedony is often used specifically to describe the white, gray, or blue translucent type of Chalcedony, but its technical term includes all additional varieties.
Onyx is an ancient gemstone, having been used in jewelry and as an ornamental gemstone for carvings since antiquity. It has traditionally been one of the most important engraving and cameo gemstones, where its most common form was a black base with a white upper layer. Although still used a minor gemstone today, the significance and value of Onyx has been diminished as compared to ancient times. When Onyx is banded black and white, it can be jointly classified as both Agate and Onyx. However, many require Onyx to have banding in roughly parallel lines, whereas other forms of Agate can have wavy or concentric forms of banding.
Source: Onyx gemstone