sedimentary

Calcite-rich limestone or travertine

Calcite, CaCO₃; likely crystalline limestone/travertine with possible aragonite

AI-generated identification · may be incorrect

White to honey-brown, earthy to pearly/vitreous luster, abundant bladed or fibrous carbonate crystals, and irregular cleavage. Calcite hardness is Mohs 3, specific gravity about 2.7, and it effervesces strongly in dilute hydrochloric acid.

Identified September 18, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed by precipitation and recrystallization of calcium carbonate, probably in a hydrothermal spring, cave, or carbonate-rich sedimentary environment. Its exact geological age cannot be determined from the image; travertine may be geologically young, while limestone can range from Precambrian to Recent.

Uses & applications

Used as decorative stone, aggregate, cement and lime feedstock; attractive crystalline pieces are collected as mineral specimens. Usually low commercial value unless crystals are exceptionally sharp, large, or well preserved.

Geological facts

The radiating, fan-like forms may represent calcite or aragonite replacing/infilling cavities or fossil-related structures. Brown coloration commonly comes from iron oxides, clay, or organic impurities.

Field identification & locations

Look for vigorous acid fizz, low hardness, and rhombohedral cleavage; calcite can scratch with a steel knife but not glass. Common settings include limestone caves, hot springs, and carbonate veins worldwide.