sedimentary

Tufa (Calcareous Tufa)

Calcareous Tufa (CaCO3)

Hardness: 3 (Mohs scale); Color: Tan, beige, or off-white; Luster: Dull to earthy; Structure: Highly porous, vesicular, or sponge-like texture; Cleavage: None (amorphous/massive); Specific Gravity: Low (1.5-2.0 due to porosity)

Hardness: 3 (Mohs scale)
Color: Tan, beige, or off-white
Luster: Dull to earthy

Identified June 20, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed by the chemical precipitation of calcium carbonate from ambient temperature water, typically in freshwater lakes, rivers, or hot springs. It often encrusts plants, moss, and debris, leaving behind vugs or holes as organic matter decays. Often associated with the Quaternary period.

Uses & applications

Historically used as a lightweight building material in arid regions; used in aquarium decor, landscaping, and as a calcium source for soil amendments.

Geological facts

Unlike travertine, which forms from hot hydrothermal waters, tufa forms from colder water. Mono Lake in California is famous for its massive tufa towers that rose from the lakebed.

Field identification & locations

Identify by its 'holey' sponge-like appearance and low density compared to other rocks. It will effervesce (fizz) vigorously if tested with dilute hydrochloric acid or vinegar because it is composed of calcite.