sedimentary
Tufa
Calcium carbonate (CaCO3) - Porous Limestone
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
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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.
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