sedimentary

Tufa

Calcium carbonate (CaCO3) - Porous Limestone

AI-generated identification · may be incorrect

Hardness: 3 on Mohs scale; Color: Tan, beige, brown, or white; Luster: Dull to earthy; Crystal structure: Microcrystalline; Cleavage: None; Specific gravity: Low (porous/lightweight)

Hardness: 3 on Mohs scale
Color: Tan, beige, brown, or white
Luster: Dull to earthy

Identified June 10, 2026More sedimentary →

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Physical properties

Hardness: 3 on Mohs scale; Color: Tan, beige, brown, or white; Luster: Dull to earthy; Crystal structure: Microcrystalline; Cleavage: None; Specific gravity: Low (porous/lightweight)

Formation & geological history

Tufa is a form of limestone created when carbonate minerals precipitate out of ambient temperature water, often near springs or lakes. It forms through both chemical precipitation and biological activity (microbialites).

Uses & applications

Commonly used in landscaping, aquariums (African Cichlid tanks), porous base for alpine gardens, and historically for lightweight construction in some regions.

Geological facts

Unlike travertine, which is formed from hot springs, tufa is a cool-water deposit. The Mono Lake Tufa State Natural Reserve in California features some of the world's most famous tufa towers.

Field identification & locations

Identify by its highly porous, spongy, or vesicular texture and light weight. It will react and fizz strongly when tested with dilute hydrochloric acid. Commonly found in Great Basin areas and limestone-rich spring environments.