sedimentary
Tufa (Calcareous Tufa)
Calcareous Tufa (Precipitated CaCO3)
Hardness: 3 (Mohs scale), Color: tan, yellowish-brown to gray, Luster: dull to earthy, Structure: porous/vesicular, Cleavage: none, Specific Gravity: low (1.5-2.0 due to porosity)
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Physical properties
Hardness: 3 (Mohs scale), Color: tan, yellowish-brown to gray, Luster: dull to earthy, Structure: porous/vesicular, Cleavage: none, Specific Gravity: low (1.5-2.0 due to porosity)
Formation & geological history
Formed by the precipitation of carbonate minerals from ambient temperature water bodies such as springs, lakes, and rivers. Often biologically mediated by algae or mosses during the Holocene or Pleistocene epochs.
Uses & applications
Used primarily in landscaping, aquascaping (African Cichlid tanks), and as a traditional lightweight building material in historical structures.
Geological facts
Tufa is often confused with Travertine; however, Tufa forms in ambient temperatures while Travertine forms in geothermal hot springs. It frequently contains imprints of organic material like leaves or twigs.
Field identification & locations
Identify by its highly porous, sponge-like appearance and its reaction (fizzing) to dilute hydrochloric acid. Commonly found near limestone springs and karst landscapes.
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