mineral

Polished banded calcite (possibly onyx marble)

Calcite, CaCO₃; exact variety is uncertain from the image

AI-generated identification · may be incorrect

Pale green, cream, and honey-colored bands with a waxy to vitreous polish; calcite has Mohs hardness 3, trigonal crystal structure, and perfect rhombohedral cleavage. The specimen’s rounded, polished shape obscures diagnostic cleavage and crystal form.

Identified September 29, 2026More mineral →

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Physical properties

Formation & geological history

Likely formed as calcite-rich layers or veins precipitated from mineral-bearing water in a cave or fracture; such deposits range widely in geological age. The stone has been cut and polished.

Uses & applications

Used for ornamental objects, carvings, and inexpensive jewelry; calcite is also an important industrial source of lime and cement, though this small specimen is primarily decorative.

Geological facts

Banded calcite is sometimes sold as “onyx” or “onyx marble,” but it is calcite, not quartz onyx. Acid causes calcite to fizz, and it can be scratched readily with a steel point.

Field identification & locations

Look for the soft hardness, pale banding, and rhombohedral cleavage; a drop of dilute acid fizzes on exposed calcite. Calcite occurs worldwide, especially in limestone caves and hydrothermal veins.