sedimentary
Tufa (Vesicular Limestone)
Tufa (form of Calcium Carbonate, CaCO3)
Hardness: 3 (Mohs scale); Color: Gray, tan, or creamy white; Luster: Dull to earthy; Structure: Highly porous, vesicular, or sponge-like texture; Specific Gravity: Low (variable due to porosity).
- Hardness
- 3 (Mohs scale)
- Color
- Gray, tan, or creamy white
- Luster
- Dull to earthy
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Physical properties
Hardness: 3 (Mohs scale); Color: Gray, tan, or creamy white; Luster: Dull to earthy; Structure: Highly porous, vesicular, or sponge-like texture; Specific Gravity: Low (variable due to porosity).
Formation & geological history
Formed by the precipitation of carbonate minerals out of ambient temperature water, often near springs or lakes. It is geologically young (Holocene to Pleistocene) compared to many other rocks.
Uses & applications
Commonly used in landscaping and garden design ('rockeries') due to its porous nature which allows moss and plants to grow on it; historically used as a lightweight building material.
Geological facts
Tufa is often confused with Travertine, but Tufa is much more porous and forms in cooler water. It can sometimes contain fossilized plant remains or snail shells trapped during the rapid precipitation process.
Field identification & locations
Identify in the field by its sponge-like appearance and light weight relative to size. It will react and fizz (effervesce) if a weak acid like vinegar is applied. Found near alkaline lakes and lime-rich springs.
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