mineral

Likely blue calcite or aragonite fragment

Calcite (CaCO₃), possibly aragonite (CaCO₃)

AI-generated identification · may be incorrect

Pale blue, translucent-to-opaque, with a dull-to-glassy luster and irregular fracture; calcite hardness is 3, aragonite 3.5–4 Mohs, and both commonly show white streak. Crystal structure is trigonal for calcite and orthorhombic for aragonite; cleavage cannot be confirmed from the photo.

Identified August 22, 2026More mineral →

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Physical properties

Formation & geological history

Usually forms from carbonate-rich groundwater, hydrothermal fluids, or sedimentary deposits; blue coloration may result from trace copper or other impurities. Its geological age is indeterminate from an isolated fragment.

Uses & applications

Calcite is used in cement, lime, construction aggregate, filler, and décor; attractive blue specimens are sold to mineral collectors. Aragonite is also used decoratively and as a carbonate raw material.

Geological facts

A drop of dilute hydrochloric acid or vinegar should produce visible fizz, especially on a freshly scratched surface. The specimen may also be dyed or surface-coated, which can intensify its blue color.

Field identification & locations

Common sources include Mexico, Peru, Morocco, Spain, and the United States. Confirm with acid reaction, hardness, cleavage, and—if needed—specific-gravity or laboratory testing; photo identification is not definitive.