sedimentary

Calcite-rich limestone (possibly crystalline limestone)

Calcite, CaCO₃, in limestone; locally recrystallized toward marble

AI-generated identification · may be incorrect

Cream to tan, coarse crystalline texture with glassy-to-pearly luster and prominent cleavage-like surfaces. Calcite has Mohs hardness 3, perfect rhombohedral cleavage, and specific gravity about 2.71; it should fizz strongly with dilute hydrochloric acid or vinegar, though impurities may reduce the reaction.

Identified September 16, 2026More sedimentary →

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Physical properties

Formation & geological history

Likely marine carbonate sediment deposited in a shallow tropical sea, later lithified and locally recrystallized by burial or mild metamorphism. The coarse crystals and pale appearance may indicate calcitic marble, but the image alone cannot distinguish it confidently from crystalline limestone.

Uses & applications

Used for cement, lime, aggregate, building stone, soil treatment, and occasionally decorative carving. Attractive pieces may be collected, but this specimen appears common rather than gem-grade.

Geological facts

Calcite commonly forms visible sparkling cleavage faces and can show birefringence. At approximately 9.9°N, 124.2°E in Bohol, Philippines, limestone and uplifted coral-carbonate formations are very plausible regional sources.

Field identification & locations

Look for vigorous acid fizz, softness relative to steel, and rhombohedral cleavage; avoid confusing it with quartz, which is harder and does not fizz. Approximate value: $1–$10 as a common hand specimen, or $10–$30 if unusually crystalline or polished.