mineral

Aragonite (specifically Mexican Marbled Onyx)

Aragonite (Calcium Carbonate, CaCO3)

Hardness: 3.5-4 (Mohs scale); Color: Creamy yellow with brownish-red banding; Luster: Vitreous to resinous; Crystal Structure: Orthorhombic; Cleavage: Distinct in one direction.

Hardness: 3
Color: Creamy yellow with brownish-red banding
Luster: Vitreous to resinous

Identified May 9, 2026More mineral →

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Physical properties

Hardness: 3.5-4 (Mohs scale); Color: Creamy yellow with brownish-red banding; Luster: Vitreous to resinous; Crystal Structure: Orthorhombic; Cleavage: Distinct in one direction.

Formation & geological history

Forms in low-temperature near-surface geological environments, often through precipitation in hot springs, caves, or marine settings. This specific carved piece is made from banded aragonite, often commercially called 'Onyx'.

Uses & applications

Used primarily in ornamental carvings, sculpture, decorative interior architecture, and as metaphysical 'healing' crystals. It is not durable enough for high-wear jewelry but excellent for figurines.

Geological facts

Despite the trade name 'Onyx', this is geologically aragonite/calcite and not true quartz-based onyx. It is soft enough to be carved with steel tools, making it popular for tourist souvenirs and decorative columns.

Field identification & locations

Identify in the field by reacting with cold dilute hydrochloric acid (it will fizz). Look for the characteristic parallel banding and translucent waxy appearance. Common in Mexico, Peru, and parts of the Middle East.

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