sedimentary
Tufa
Calcareous Tufa (Calcium carbonate, CaCO3)
Hardness: 3-4 (Mohs); Color: tan, cream, gray, or white; Luster: earthy to dull; Structure: highly porous and cellular; Cleavage: none (microcrystalline)
- Hardness
- 3-4 (Mohs)
- Color
- tan, cream, gray, or white
- Luster
- earthy to dull
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Physical properties
Hardness: 3-4 (Mohs); Color: tan, cream, gray, or white; Luster: earthy to dull; Structure: highly porous and cellular; Cleavage: none (microcrystalline)
Formation & geological history
Formed by the precipitation of carbonate minerals from ambient temperature water, often near hot springs or alkaline lakes, where evaporation or degassing of CO2 occurs. Typically Holocene to Pleistocene in age.
Uses & applications
Commonly used in landscaping and rock gardens due to its aesthetic texture and light weight. Historically used as a building material in semi-arid regions.
Geological facts
Unlike travertine, which forms from hot geothermal water, tufa forms from water at cooler temperatures and often incorporates plant matter or algae into its porous structure during formation.
Field identification & locations
Identified by its extremely lightweight, pitted, sponge-like appearance and chemical reaction (fizzing) with diluted hydrochloric acid. Commonly found around alkaline lakes like Mono Lake, California, or historical lake beds.
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