mineral
Likely blue calcite or aragonite fragment
Calcite (CaCO₃), possibly aragonite (CaCO₃)
AI-generated identification · may be incorrectPale 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.
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Physical properties
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.
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.
