sedimentary

White Onyx (Marble Onyx)

Calcite (CaCO3) - Banded Calcium Carbonate

Hardness: 3 on Mohs scale; Color: Translucent white to cream with snowy veining; Luster: Vitreous to waxy; Crystal Structure: Trigonal/Hexagonal; Cleavage: Perfect rhombohedral; Specific Gravity: 2.71

Hardness: 3 on Mohs scale
Color: Translucent white to cream with snowy veining
Luster: Vitreous to waxy

Identified March 7, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed in caves through the slow precipitation of calcium carbonate from dripping cold-water springs or groundwater (speleothems). Unlike true onyx (silica-based), this is a chemical sedimentary rock mostly from the Quaternary period.

Uses & applications

Used extensively in interior design for backlit countertops, wall accents, and decorative carvings. Also used in luxury furniture, small ornaments, and holistic 'crystal healing' practices.

Geological facts

Despite its trade name 'White Onyx', it is geologically a type of marble or travertine rather than true onyx (which is chalcedony). It is highly prized for its extreme translucency which allows light to pass through the stone.

Field identification & locations

Identify in the field by its softness (it can be scratched by a copper coin or steel knife) and its reaction (fizzing) to diluted hydrochloric acid. Common locations include Mexico, Iran, Turkey, and Pakistan.

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