sedimentary

Calcareous Tufa (Tufa)

Precipitated Calcium Carbonate (CaCO3)

AI-generated identification · may be incorrect

Hardness: 3 on the Mohs scale; Color: tan, cream, pale beige, to light brown; Luster: earthy, dull; Crystal Structure: trigonal (microcrystalline calcite); Cleavage: rhombohedral in individual microcrystals, though massive and highly porous/spongy in aggregate form; Specific Gravity: ~1.5 - 2.5 (due to high porosity)

Hardness: 3 on the Mohs scale
Color: tan, cream, pale beige, to light brown
Luster: earthy, dull

Identified October 17, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed by the rapid precipitation of calcium carbonate (calcite) from ambient temperature water, often around springs, lake shores, or waterfalls, frequently encrusting organic matter such as mosses and twigs.

Uses & applications

Used historically as a lightweight construction stone, in alpine rock gardens due to its moisture-retaining porosity, and as a natural geological specimen.

Geological facts

Tufa often traps and fossilizes leaves, stems, and shells, preserving exquisite hollow casts of the vegetation around which it precipitated.

Field identification & locations

Identified in the field by its porous, cellular texture, light weight relative to solid limestone, and strong effervescence when exposed to dilute hydrochloric acid. Commonly found in karst regions and alkaline lake basins such as Mono Lake, California.