mineral
Tumbled pale-green mineral specimen, likely calcite or prehnite
Probably calcite (CaCO₃) or prehnite (Ca₂Al₂Si₃O₁₀(OH)₂); exact identification requires testing
AI-generated identification · may be incorrectPale mint-green to whitish, translucent, with a dull-to-vitreous luster and granular crystalline texture. Calcite has Mohs hardness 3, rhombohedral cleavage, and fizzes in dilute hydrochloric acid; prehnite is harder (6–6.5) and does not readily fizz.
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Physical properties
Pale mint-green to whitish, translucent, with a dull-to-vitreous luster and granular crystalline texture. Calcite has Mohs hardness 3, rhombohedral cleavage, and fizzes in dilute hydrochloric acid; prehnite is harder (6–6.5) and does not readily fizz.
Formation & geological history
Likely a hydrothermal or cavity-forming mineral from altered volcanic rock; calcite commonly forms in veins and cavities, while prehnite forms in low-temperature basalt alteration zones. Geological age is locality-dependent, commonly Mesozoic to recent.
Uses & applications
Mostly used as a collectible or lapidary specimen; calcite has major industrial uses in cement, lime, and filler, while prehnite is occasionally cut as a gemstone.
Geological facts
The rounded edges indicate tumbling or natural abrasion. Color alone is insufficient for reliable identification because pale-green calcite, prehnite, chrysoprase, and quartz can look similar.
Field identification & locations
Test hardness against a steel knife and apply dilute vinegar or hydrochloric acid to a hidden spot; effervescence strongly supports calcite. Common sources include Mexico, Brazil, India, South Africa, and the United States.
