mineral
Tumbled orange-and-white calcite
Calcite (calcium carbonate, CaCO₃)
AI-generated identification · may be incorrectTypically Mohs hardness 3, vitreous to pearly luster, white to honey-orange color, translucent in places, and rhombohedral cleavage; the rounded shape indicates tumbling or natural water wear. Effervesces strongly with dilute hydrochloric acid or vinegar, though vinegar may react slowly.
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Physical properties
Typically Mohs hardness 3, vitreous to pearly luster, white to honey-orange color, translucent in places, and rhombohedral cleavage; the rounded shape indicates tumbling or natural water wear. Effervesces strongly with dilute hydrochloric acid or vinegar, though vinegar may react slowly.
Formation & geological history
Forms in limestone, hydrothermal veins, caves, and evaporite environments through precipitation from carbonate-rich water; specimens may range from ancient sedimentary settings to recent cave deposits. Orange coloration commonly comes from iron-oxide inclusions or impurities.
Uses & applications
Used industrially for cement, lime, agricultural soil treatment, and construction aggregate; attractive transparent or banded pieces are collected and occasionally carved. This specimen has modest decorative value.
Geological facts
Calcite is one of the most abundant carbonate minerals and displays strong birefringence, producing a doubled image through clear pieces. It is softer and more reactive than quartz, despite sometimes resembling it.
Field identification & locations
Identify by its softness, rhombohedral cleavage, and acid reaction; common sources include Mexico, the United States, Iceland, Brazil, and China. Avoid prolonged soaking in acids, which dulls and dissolves the surface.
