mineral

Massive calcite (likely limestone-derived calcite)

Calcite, calcium carbonate (CaCO₃); possibly a chalky limestone fragment

AI-generated identification · may be incorrect

White to cream, opaque, earthy to vitreous luster, irregular granular texture, and no obvious crystal faces. Calcite has Mohs hardness 3, perfect rhombohedral cleavage, specific gravity about 2.71, and effervesces strongly with dilute hydrochloric acid or vinegar (more slowly).

Identified September 22, 2026More mineral →

Explore Massive calcite (likely limestone-derived calcite) in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Forms by precipitation from carbonate-rich water, biological accumulation, or alteration of limestone; specimens may range from recent deposits to Paleozoic–Mesozoic sedimentary rocks. The image alone cannot establish its exact age or whether it is pure calcite versus limestone.

Uses & applications

Used in cement, lime, aggregate, soil treatment, glass manufacture, and industrial fillers; clear crystals are collected, but this rough piece has little jewelry value.

Geological facts

Calcite is one of the most abundant carbonate minerals and commonly occurs as rhombohedra, scalenohedra, or massive chalky material. Double refraction is visible through clear calcite crystals.

Field identification & locations

Likely from a limestone, marble, cave, or carbonate vein. Confirm with acid fizz, a scratch test against a copper coin or steel nail, and inspection for rhombohedral cleavage; dolomite reacts weakly unless powdered.