metamorphic

Rounded calcite-rich limestone or marble pebble

Calcite (CaCO₃), likely recrystallized limestone (marble)

AI-generated identification · may be incorrect

Cream-white, translucent to opaque, with a sugary crystalline texture and vitreous to pearly luster. Calcite has Mohs hardness 3, perfect rhombohedral cleavage, and specific gravity about 2.71; it effervesces strongly in dilute hydrochloric acid.

Identified September 10, 2026More metamorphic →

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Physical properties

Formation & geological history

Likely formed from marine carbonate sediment that lithified as limestone and may later have recrystallized during low-grade metamorphism; exact geological age cannot be determined from the photograph. Its rounded shape indicates stream, beach, or deliberate tumbling abrasion.

Uses & applications

Common calcite/limestone is used for cement, lime, aggregate, soil treatment, and ornamental stone; attractive polished pieces are inexpensive curios or educational specimens.

Geological facts

Calcite is one of Earth’s most abundant carbonate minerals and exhibits strong birefringence, producing doubled images through clear crystals.

Field identification & locations

Test with dilute acid, inspect for rhombohedral cleavage, and compare hardness against a copper coin; marble is typically harder-looking and more sugary than ordinary limestone. Common worldwide, especially in carbonate terrains and metamorphic belts.