mineral
Tumbled blue stone, likely blue calcite
Calcite (CaCO₃), blue variety; identification is provisional from the image
AI-generated identification · may be incorrectOpaque blue to blue-gray, waxy-to-dull luster, rounded tumbled shape, and likely Mohs hardness 3; calcite has rhombohedral cleavage and specific gravity about 2.71. The cloudy mottling is consistent with blue calcite, though blue apatite or dyed material are alternatives.
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Physical properties
Opaque blue to blue-gray, waxy-to-dull luster, rounded tumbled shape, and likely Mohs hardness 3; calcite has rhombohedral cleavage and specific gravity about 2.71. The cloudy mottling is consistent with blue calcite, though blue apatite or dyed material are alternatives.
Formation & geological history
Blue calcite forms in hydrothermal veins and carbonate rocks, commonly through impurities such as copper or other trace elements; its age depends on the host deposit. Tumbled specimens are human-polished geological material.
Uses & applications
Used mainly as a decorative stone, lapidary material, and mineral-collection specimen; it is generally unsuitable for durable jewelry because of low hardness and cleavage.
Geological facts
Calcite effervesces visibly with dilute hydrochloric acid, unlike most blue apatite; it can also be scratched by a steel knife. Color alone cannot confirm the variety.
Field identification & locations
Common sources include Mexico, Argentina, Madagascar, and parts of the United States; inspect for softness, cleavage, and acid reaction. A refractive-index or hardness test can distinguish it from apatite.
