mineral
Mixed rough mineral specimens, likely calcite with prehnite/zeolite
Calcite (CaCO₃), with probable prehnite (Ca₂Al₂Si₃O₁₀(OH)₂) and/or zeolite-group minerals
AI-generated identification · may be incorrectPale green, cream, and white translucent pieces with vitreous to pearly luster, uneven-to-cleavage surfaces, and granular or botryoidal textures. Calcite is Mohs 3 with rhombohedral cleavage; prehnite is Mohs 6–6.5 and commonly pale green.…
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Physical properties
Pale green, cream, and white translucent pieces with vitreous to pearly luster, uneven-to-cleavage surfaces, and granular or botryoidal textures. Calcite is Mohs 3 with rhombohedral cleavage; prehnite is Mohs 6–6.5 and commonly pale green. The porous brown-white piece may be a weathered zeolite or coral-like carbonate, but cannot be identified confidently from the image alone.
Formation & geological history
These are likely low-temperature hydrothermal or cavity minerals formed in volcanic-rock vesicles and fractures; calcite may also be sedimentary or vein-forming. Geological ages are locality-dependent, commonly Cenozoic to Mesozoic for such deposits.
Uses & applications
Mostly sold as inexpensive study or decorative specimens; calcite and zeolites have industrial uses, while attractive prehnite may be cut for cabochons. Not suitable for structural construction as pictured.
Geological facts
Green color alone is not diagnostic: prehnite, fluorite, apophyllite, and green calcite can look similar. A vinegar or dilute hydrochloric-acid test that effervesces identifies calcite, but may damage specimens.
Field identification & locations
Likely sources include India, Brazil, China, Mexico, and volcanic regions worldwide. Confirm with hardness, acid reaction, cleavage, and a loupe; testing individual pieces is necessary because this is a mixed lot.
