sedimentary

Tufa

Calcareous Tufa (Calcium Carbonate, CaCO3)

AI-generated identification · may be incorrect

Hardness: 3 on Mohs scale; Color: Cream, tan, or grey; Luster: Dull/Earthy; Structure: Highly porous, vesicular, or sponge-like structure with no visible crystals; Specific Gravity: Low due to porosity.

Hardness: 3 on Mohs scale
Color: Cream, tan, or grey
Luster: Dull/Earthy

Identified February 19, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed by the precipitation of carbonate minerals from ambient temperature water bodies, often around hot springs or lake shores. It is chemically precipitated rather than being formed from organic debris or extreme heat/pressure.

Uses & applications

Historically used as a building material in ancient architecture; currently used in landscaping, as an aquarium substrate to buffer pH, and as a lightweight aggregate in mortar.

Geological facts

Tufa is often confused with travertine, but tufa is much more porous and forms in cooler water. Famous tufa structures include the massive 'tufa towers' at Mono Lake, California.

Field identification & locations

Identify in the field by its sponge-like appearance and light weight. It will react and fizz (effervesce) if a weak acid like vinegar is applied. Commonly found in Great Basin areas and near limestone-rich spring water.