Travertine

Physical Properties

Hardness: 3-4 (Mohs); Color: Tan, reddish-brown, cream; Luster: Dull to earthy; Structure: Highly porous, vesicular, or concretionary; Cleavage: None (conchoidal fracture)

Formation & Geological History

Formed by the rapid precipitation of calcium carbonate, often at the mouth of hot springs or in limestone caves. The porous texture is caused by gas bubbles being trapped during formation.

Uses & Applications

Used primarily as building stone, floor tiles, and garden decoration. Historically used for monuments like the Roman Colosseum.

Geological Facts

This specimen appears to be a 'calcareous tufa' or travertine, which often traps plant matter or shells within its rapidly growing structure. Some of the largest travertine deposits are found in Yellowstone National Park at Mammoth Hot Springs.

Field Identification & Locations

Identify by its 'bubbly' or hole-filled appearance and its reaction (fizzing) with diluted hydrochloric acid. Common in geothermal areas and limestone regions.

Identified on: 4/23/2026

Mode: Standard