sedimentary

Tufa

Calcareous Tufa (Calcium carbonate, CaCO3)

AI-generated identification · may be incorrect

Hardness: 3-4 (Mohs); Color: tan, cream, gray, or white; Luster: earthy to dull; Structure: highly porous and cellular; Cleavage: none (microcrystalline)

Hardness: 3-4 (Mohs)
Color: tan, cream, gray, or white
Luster: earthy to dull

Identified June 28, 2026More sedimentary →

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Physical properties

Hardness: 3-4 (Mohs); Color: tan, cream, gray, or white; Luster: earthy to dull; Structure: highly porous and cellular; Cleavage: none (microcrystalline)

Formation & geological history

Formed by the precipitation of carbonate minerals from ambient temperature water, often near hot springs or alkaline lakes, where evaporation or degassing of CO2 occurs. Typically Holocene to Pleistocene in age.

Uses & applications

Commonly used in landscaping and rock gardens due to its aesthetic texture and light weight. Historically used as a building material in semi-arid regions.

Geological facts

Unlike travertine, which forms from hot geothermal water, tufa forms from water at cooler temperatures and often incorporates plant matter or algae into its porous structure during formation.

Field identification & locations

Identified by its extremely lightweight, pitted, sponge-like appearance and chemical reaction (fizzing) with diluted hydrochloric acid. Commonly found around alkaline lakes like Mono Lake, California, or historical lake beds.