Onyx is a banded variety of chalcedony, a cryptocrystalline form of silica belonging to the quartz family. It is known for its striking parallel bands of alternating colors, such as black and white or red and brown. The fine-grained texture and glassy luster of onyx make it highly desirable as a decorative stone and gemstone for jewelry and ornamental objects.

Mineral Makeup

Onyx is composed primarily of silica in the form of chalcedony, a cryptocrystalline quartz. The characteristic bands of onyx are created by the presence of impurities, such as iron and manganese, which create varying colors in the chalcedony. The black color in onyx is often due to the presence of carbon or organic material.


Onyx forms in the cavities and fissures of volcanic rocks and limestone, where silica-rich fluids deposit layers of chalcedony. Over time, the silica-rich fluids become saturated with various impurities, resulting in the formation of the distinct, parallel bands that define onyx.


As a gemstone, onyx is prized for its unique banding patterns and rich colors. It is often used in making jewelry such as rings, necklaces, and bracelets. The alternating color bands make it especially appealing for carving cameos and intaglios, where the contrasting layers can create intricate designs and portraits. Onyx gemstones are also believed to hold protective properties, which contribute to their popularity in amulets and talismans.


Onyx can be found worldwide, with notable deposits in Brazil, India, Madagascar, Mexico, and the United States. Its unique banding patterns and rich colors make it a popular choice for jewelry and decorative objects, especially in carved cameos and intaglios.


Onyx is believed to possess metaphysical properties that promote grounding, strength, and self-control. It is said to help individuals overcome negative emotions, such as fear and anxiety, and provide support during times of stress or grief. Onyx is also associated with protection, making it a popular choice for amulets and talismans.

ClassSedimentary (Chemical)
FormulaSilica, with impurities such as iron, manganese, and carbon 
LusterVitreous to waxy
Hardness (Mohs)6.5-7
ColorBanded with alternating colors, typically black and white or red and brown 
Specific Gravity2.58-2.64