mineral
Blue calcite geode
Calcite (CaCO₃), commonly a druse-lined geode
AI-generated identification · may be incorrectPale blue-gray, translucent to transparent calcite crystals with pearly-to-glassy luster and prominent rhombohedral cleavage; Mohs hardness 3, specific gravity about 2.71. The crystals appear blocky/rhombohedral rather than quartz-like hexagonal prisms.
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Physical properties
Pale blue-gray, translucent to transparent calcite crystals with pearly-to-glassy luster and prominent rhombohedral cleavage; Mohs hardness 3, specific gravity about 2.71. The crystals appear blocky/rhombohedral rather than quartz-like hexagonal prisms.
Formation & geological history
Likely formed when carbonate-rich groundwater deposited calcite crystals inside a cavity in volcanic or sedimentary host rock; the specimen itself cannot establish a precise age, but such deposits range from young to millions of years old.
Uses & applications
Used mainly as a decorative and collectible specimen; calcite is also an important industrial source of lime and carbonate for cement, aggregate, glass, and chemical products.
Geological facts
Calcite shows strong birefringence: printed text viewed through a clear fragment may appear doubled. Blue coloration can result from trace impurities, inclusions, or irradiation-related defects.
Field identification & locations
Identify by its rhombohedral cleavage, softness, vigorous fizz with dilute hydrochloric acid, and lack of quartz’s hardness. Blue calcite specimens occur in Mexico, South America, the United States, and other carbonate-bearing regions.
