sedimentary

Limestone (Travertine/Tufa variant)

Calcium Carbonate (CaCO3)

Hardness: 3 (Mohs scale); Color: Cream, tan, greyish-white; Luster: Dull to earthy; Crystal structure: Trigonal (microcrystalline calcite); Cleavage: Perfect rhombohedral in crystals, but not visible in massive form; Specific Gravity: 2.5-2.7

Hardness: 3 (Mohs scale)
Color: Cream, tan, greyish-white
Luster: Dull to earthy

Identified July 5, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed by the precipitation of calcium carbonate from mineral springs (terrestrial) or organic accumulation in marine environments. The porous, pitted surface suggests a karst environment or exposure to chemical weathering over thousands of years.

Uses & applications

Used extensively in construction as building stone, aggregate for concrete, production of cement, and as a soil conditioner in agriculture.

Geological facts

Limestone accounts for about 10% of the total volume of all sedimentary rocks. It is the primary host for the world's most impressive cave systems and is essential for the production of quicklime.

Field identification & locations

Identify in the field by its reaction to dilute hydrochloric acid (effervescence). Look for pitted 'vuggy' textures and fossils. Found worldwide, especially in areas with ancient seabed exposure like the Midwest USA or Southern Europe.

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