sedimentary
Travertine (often colloquially called Tufa)
Chemical Sedimentary Calcium Carbonate (CaCO3)
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
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Physical properties
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).
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.
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