sedimentary
Limestone (Tufa/Travertine)
Sedimentary Calcium Carbonate (CaCO3)
Hardness: 3 on Mohs scale; Color: Tan, beige, or white; Luster: Dull to earthy; Crystal structure: Trigonal (microcrystalline calcite); Specific gravity: 2.5-2.7. Often porous or vesicular in texture.
- Hardness
- 3 on Mohs scale
- Color
- Tan, beige, or white
- Luster
- Dull to earthy
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Physical properties
Hardness: 3 on Mohs scale; Color: Tan, beige, or white; Luster: Dull to earthy; Crystal structure: Trigonal (microcrystalline calcite); Specific gravity: 2.5-2.7. Often porous or vesicular in texture.
Formation & geological history
Formed by the precipitation of carbonate minerals from ambient temperature water bodies (tufa) or hot springs (travertine). It often forms in lacustrine, fluvial, or spring environments where evaporation or CO2 degassing occurs.
Uses & applications
Used in construction, as a building stone (travertine), in the production of lime and cement, and occasionally as decorative garden stone due to its unique weathered texture.
Geological facts
Tufa towers in Mono Lake, California, are famous examples of this rock type. It can often encapsulate organic remains like leaves or twigs, preserving their shapes as fossils.
Field identification & locations
Identify in the field by its porous, 'sponge-like' appearance and its strong effervescence when exposed to a drop of dilute hydrochloric acid. Commonly found near calcareous springs or dried lake beds.
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