sedimentary

Travertine (often colloquially called Tufa)

Chemical Sedimentary Calcium Carbonate (CaCO3)

AI-generated identification · may be incorrect

Hardness: 3-4 (Mohs scale); Color: Tan, beige, off-white, or brownish; Luster: Dull to earthy; Crystal Structure: Trigonal (as microcrystalline calcite); Cleavage: Perfect rhombohedral (but usually not visible in massive forms); Specific Gravity: 2.5–2.7 (though may feel lighter due to porosity).

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

Identified March 26, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed by the rapid precipitation of calcium carbonate, often at the mouth of hot springs or in limestone caves (as stalactites/stalagmites). The porous texture often results from the presence of gas bubbles or the encrustation of organic matter like moss or algae during rapid mineralization.

Uses & applications

Extensively used in construction as building stone for facades, flooring, and garden paths. In the ornamental industry, it is used for sculptures, vases, and interior design accents. It is also a source of lime for industrial processes.

Geological facts

Famous for being the primary building material of the Roman Colosseum. Unlike most sedimentary rocks, it forms relatively quickly on a geological timescale through chemical evaporation rather than long-term lithification of sand or mud.

Field identification & locations

Identify in the field by its characteristic pitted, porous surface and its vigorous reaction (fizzing) when exposed to a drop of weak hydrochloric acid (the 'acid test'). It is commonly found in geothermal areas like Yellowstone or Tivoli, Italy.