mineral
Tumbled blue-green calcite
Calcite (calcium carbonate, CaCO₃), likely blue or pale aqua variety
AI-generated identification · may be incorrectMohs hardness 3; pale aqua-white, translucent, with a waxy to vitreous luster and irregular tumbled surfaces. Trigonal crystal system; excellent rhombohedral cleavage, though cleavage is obscured by polishing; specific gravity about 2.71.
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Physical properties
Mohs hardness 3; pale aqua-white, translucent, with a waxy to vitreous luster and irregular tumbled surfaces. Trigonal crystal system; excellent rhombohedral cleavage, though cleavage is obscured by polishing; specific gravity about 2.71.
Formation & geological history
Calcite commonly forms in hydrothermal veins, limestone, marble, and cavities. Blue coloration may result from trace impurities; its age depends on the original deposit and cannot be determined from the image.
Uses & applications
Used for cement, lime, aggregate, and neutralizing acids; attractive translucent pieces are sold as inexpensive decorative or metaphysical specimens. It is too soft for most durable jewelry.
Geological facts
Calcite effervesces strongly in dilute hydrochloric acid and can be scratched easily with a steel knife. Blue calcite is often confused with aragonite or dyed chalcedony.
Field identification & locations
Likely identified by its very low hardness, pale blue color, and acid reaction; verify with a scratch test on an inconspicuous area and acid only if damage is acceptable. Common worldwide, especially in limestone and hydrothermal regions.
