mineral

Blue calcite geode

Calcite (CaCO₃), commonly a druse-lined geode

AI-generated identification · may be incorrect

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.

Identified August 30, 2026More mineral →

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Physical properties

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.