Black onyx is a variety of chalcedony, a mineral in the quartz family, that is characterized by its solid black color and smooth, polished surface. It is a popular gemstone for both men's and women's jewelry due to its striking appearance and durability. Black onyx is believed to have grounding and protective properties, and is often used for spiritual and healing purposes. It is said to promote strength and resilience, as well as enhance focus and determination. Black onyx is found in many locations around the world, including Brazil, India, and Madagascar. It is often used in rings, bracelets, and necklaces, and is a popular stone for men's signet rings.