Onyx is a type of chalcedony that is typically black or dark brown in color. It is a popular gemstone that is often used in jewelry and other decorative items.
Onyx is formed when silica-rich water seeps into cracks and cavities in rocks. As the water evaporates, the silica crystals grow and form a solid mass. The color of onyx is determined by the presence of impurities, such as iron or manganese.
