mineral

Banded calcite (onyx marble)

Calcite, CaCO₃; commonly sold as “honey onyx” or “Mexican onyx”

AI-generated identification · may be incorrect

Cream, honey, and translucent-brown curved banding with vitreous to pearly luster; Mohs hardness 3, rhombohedral crystal structure, perfect rhombohedral cleavage, and specific gravity about 2.71. The layered appearance is characteristic of banded calcite rather than true quartz onyx.

Identified September 12, 2026More mineral →

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Physical properties

Formation & geological history

Forms when calcium-carbonate-rich groundwater precipitates in caves, springs, or cavities, producing successive flow bands; deposits are generally geologically young compared with many crystalline marbles. The dark gray coating may be residual host rock or surface alteration.

Uses & applications

Used for ornamental stone, carvings, tabletops, decorative slabs, and inexpensive polished specimens; it is too soft for most durable jewelry. Avoid acids, abrasion, and harsh cleaners.

Geological facts

Calcite effervesces strongly with dilute hydrochloric acid or vinegar, especially on a freshly scratched surface. “Onyx marble” is a commercial name and is not true silica onyx.

Field identification & locations

Common sources include Mexico, Turkey, Pakistan, Afghanistan, and parts of the United States. Identify it by softness, cleavage, curved translucent banding, and acid reaction; a steel knife can scratch it.