sedimentary

Tufa

Calcareous Tufa (CaCO3)

Hardness: 3-4 (Mohs); Color: Tan, beige, or grayish-white; Luster: Dull to earthy; Texture: Highly porous and vesicular with vugs; Structure: Microcrystalline calcite.

Hardness: 3-4 (Mohs)
Color: Tan, beige, or grayish-white
Luster: Dull to earthy

Identified July 19, 2026More sedimentary →

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Physical properties

Hardness: 3-4 (Mohs); Color: Tan, beige, or grayish-white; Luster: Dull to earthy; Texture: Highly porous and vesicular with vugs; Structure: Microcrystalline calcite.

Formation & geological history

Formed by the precipitation of carbonate minerals from ambient temperature water bodies, typically in freshwater lakes or near mineral springs and waterfalls. Often includes trapped organic matter.

Uses & applications

Historically used as a lightweight building stone in architecture (e.g., in Rome) and highly popular in gardening and aquarium aquascaping due to its porous nature.

Geological facts

Mono Lake in California is famous for its giant tufa towers. Tufa is often confused with travertine, but it is much more porous and forms in cooler water environments.

Field identification & locations

Identify by its light weight, 'sponge-like' appearance, and positive reaction (fizzing) to diluted hydrochloric acid. Common in karst landscapes and alkaline lakes.