sedimentary

Banded calcite (travertine or calcite-rich carbonate)

Calcite, CaCO₃; likely banded travertine or recrystallized limestone

AI-generated identification · may be incorrect

White, cream, gray, and brown curved bands with a sugary to crystalline luster; calcite has Mohs hardness 3, rhombohedral cleavage, and specific gravity about 2.71. Effervesces strongly with dilute hydrochloric acid or vinegar, especially on a fresh surface.

Identified August 13, 2026More sedimentary →

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Physical properties

Formation & geological history

Likely formed by precipitation of calcium carbonate from mineral-rich groundwater or hot springs, producing layered travertine; alternatively it may be recrystallized limestone. Such deposits can form from recent geologic time to millions of years old.

Uses & applications

Used as decorative stone, ornamental slabs, and aggregate; attractive pieces are collected, though this specimen appears relatively common and unpolished.

Geological facts

The sweeping concentric banding records changing water chemistry and flow conditions. Brown coloration commonly comes from iron oxides, clay, or organic impurities.

Field identification & locations

Look for very low hardness, rhombohedral cleavage, and acid fizzing; do not confuse it with quartz, which is much harder and does not react with acid. Common sources include Turkey, Iran, Mexico, Italy, and U.S. hot-spring or cave deposits.