sedimentary

Banded onyx (decorative calcite/aragonite)

Travertine or cave-deposit calcite, CaCO₃ (often commercially called onyx marble)

AI-generated identification · may be incorrect

Typically Mohs hardness 3–4, translucent cream, honey, gray, and brown bands, with vitreous to pearly luster and strong calcite cleavage; composed mainly of fibrous or crystalline calcite, sometimes aragonite. Effervesces vigorously with dilute hydrochloric acid.

Identified August 26, 2026More sedimentary →

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At a glance

Common name: Banded onyx (decorative calcite/aragonite)
Scientific name: Travertine or cave-deposit calcite, CaCO₃ (often commercially called onyx marble)
Category: sedimentary
Identified: August 26, 2026
Method: Standard

AI Estimated Value

Approximately $50–$300 for a specimen this size and quality; exceptional polished or highly translucent pieces may sell for $500–$1,000+.

Not an official valuation

AI estimate for general interest only — not an appraisal. Actual value depends on condition, provenance, and market demand. Verify with a professional before buying, selling, or insuring.

This identification was generated by AI and may contain errors. Verify important details before relying on them — and never use an AI result to judge whether a specimen is safe to handle. Read the full disclaimer

Physical properties

Formation & geological history

Forms when mineral-rich groundwater precipitates carbonate in caves, springs, or fissures; color bands reflect changing impurities and flow conditions. Deposits are generally Quaternary to Cenozoic, though similar banded carbonate can be older.

Uses & applications

Used for carved ornaments, polished slabs, countertops, lamps, and architectural decoration; softer than quartz onyx and unsuitable for heavy-wear applications. Decorative specimens commonly have moderate collector value.

Geological facts

The pictured flowing concentric patterns are characteristic of “onyx marble,” a trade term unrelated to true quartz onyx. Translucent layers can glow dramatically when backlit.

Field identification & locations

Identify by its layered, waxy appearance, softness, and acid reaction; it commonly comes from Mexico, Pakistan, Turkey, Iran, and Italy. Avoid vinegar testing on valuable pieces because it can etch the surface.