sedimentary

Calcareous Tufa

Tufa (Calcium Carbonate, CaCO3)

Hardness: 3 (Mohs scale); Color: Tan, beige, or yellowish-white; Luster: Dull or earthy; Texture: Highly porous and vesicular; Crystal Structure: Trigonal (microcrystalline calcite).

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

Identified July 17, 2026More sedimentary →

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Physical properties

Hardness: 3 (Mohs scale); Color: Tan, beige, or yellowish-white; Luster: Dull or earthy; Texture: Highly porous and vesicular; Crystal Structure: Trigonal (microcrystalline calcite).

Formation & geological history

Formed through the precipitation of carbonate minerals from ambient temperature water, often in rivers, lakes, or near hot springs. It commonly forms around vegetation or organic debris, which later decays to leave behind a porous structure.

Uses & applications

Historically used as a construction material (especially in Rome) due to its light weight and insulating properties. Currently used in landscaping, aquascaping, and as a soil amendment to neutralize acidity.

Geological facts

Tufa is often confused with Travertine; however, Tufa is formed at ambient temperatures and is much more porous, whereas Travertine is formed in geothermal hot springs and is denser.

Field identification & locations

Identify in the field by its extreme porosity, lightweight feel compared to limestone, and its vigorous reaction (effervescence) when a drop of diluted hydrochloric acid is applied. Found worldwide near lime-rich water sources.