mineral

Weathered blue-gray calcite/aragonite fragment

Calcium carbonate (CaCO₃), probably calcite; possibly shell-derived aragonite

AI-generated identification · may be incorrect

Soft, pale blue-gray, earthy to dull luster with whitish porous interior; hardness about 3 (calcite) or 3.5–4 (aragonite), brittle, with cleavage more likely if calcite. Effervesces strongly with dilute hydrochloric acid or vinegar, though the apparent blue coating may be surface staining or weathering.

Identified August 10, 2026More mineral →

Explore Weathered blue-gray calcite/aragonite fragment 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

Likely a weathered carbonate fragment from limestone, shell, or cemented marine material; geological age and exact source cannot be determined from the image. Carbonate minerals commonly form in shallow marine sediments, caves, veins, and altered limestones.

Uses & applications

Usually limited to teaching, collecting, or lapidary use; calcite and limestone are widely used for cement, aggregate, lime, and neutralizing acidic soils, but this small specimen has negligible commercial value.

Geological facts

The blue color is atypical for fresh calcite and may result from copper-bearing staining, dye, or an altered coating. The porous cream-colored interior suggests shell or limestone rather than a transparent crystal.

Field identification & locations

Found commonly in limestone, beach, quarry, and construction-fill environments; test with acid, inspect for shell layering, and check whether the blue surface scratches or flakes. Exact identification requires hardness, acid, and microscopy tests.