Onyx is a natural stone recognized by its parallel bands of varying colors. It is a form of chalcedony, a cryptocrystalline variety of quartz. Valued for centuries, its visual appeal and layered appearance have made it a sought-after material for jewelry, carvings, and decorative items.
Global Sources and Mining Regions
Onyx deposits are found across the globe, with significant mining operations in several countries. Mexico is a prominent source, particularly known for “Mexican onyx” from regions like Puebla and Oaxaca. This type often displays warm, honey-like tones and reddish hues.
Brazil is another leading producer, with mines primarily in the southern states of Rio Grande do Sul and Bahia, yielding classic black and white banded varieties, as well as green and red colored onyx. Pakistan’s Balochistan province is a major contributor, notably for its Sulemani onyx, which features striking black and white bands, and vibrant green and pink variations. India, with deposits in Madhya Pradesh, Rajasthan, Gujarat, and Maharashtra, is also a top source for onyx with clear black and white banding.
Other countries contributing to the global supply include Uruguay, Argentina, Australia, Canada, China, Czech Republic, Germany, Greece, Indonesia, Madagascar, Turkey (especially Afyon and Nevsehir), Iran (Esfahan), Yemen, and various states within the United States, such as Arizona, California, and Utah.
The Geological Story of Onyx Formation
True onyx primarily forms through the deposition of silica-rich solutions within cavities and fractures in rocks. This process often occurs in areas with volcanic activity, where groundwater carrying dissolved silica infiltrates existing rock formations. Over time, this silica precipitates in rhythmic layers, gradually forming the cryptocrystalline quartz structure that characterizes onyx. The distinct parallel banding, which differentiates it from agate’s curved patterns, arises from changes in the concentration or composition of these silica solutions, or the presence of varying mineral impurities like iron and manganese during formation.
A material also commonly referred to as “onyx,” such as “Mexican onyx” or “cave onyx,” forms through a different geological process. This material is a type of banded calcium carbonate, specifically travertine or banded calcite. It develops in limestone caves as stalactitic and stalagmitic formations, or from mineral-rich warm waters emerging from fissures and faults. The slow dripping of water saturated with calcium carbonate results in the deposition of successive layers, creating its characteristic bands.
Onyx in Everyday Applications
Onyx is widely used in a variety of applications due to its visual appeal and physical properties. In jewelry, it is frequently fashioned into rings, bracelets, earrings, and necklaces, often cut as cabochons or carved into beads. Its smooth finish and ability to be polished to a high sheen make it suitable for intricate designs, including intaglios and cameos.
Beyond personal adornment, onyx serves as a popular material for decorative items. It is carved into sculptures, figurines, vases, lamps, and chess sets, adding elegance to interior spaces. In architecture and interior design, onyx is utilized for tiles, countertops, wall panels, and flooring. Its translucent quality allows light to pass through, making it a favored choice for backlit features that create a dramatic visual effect in various settings.