mineral
Calcite
Calcite (CaCO₃), likely massive crystalline calcite
AI-generated identification · may be incorrectUsually white to cream with pearly-to-glassy luster; Mohs hardness 3, perfect rhombohedral cleavage, and commonly translucent. It effervesces vigorously in dilute hydrochloric acid or strong vinegar, though vinegar may react slowly.
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Physical properties
Usually white to cream with pearly-to-glassy luster; Mohs hardness 3, perfect rhombohedral cleavage, and commonly translucent. It effervesces vigorously in dilute hydrochloric acid or strong vinegar, though vinegar may react slowly.
Formation & geological history
Forms in limestone, marble, hydrothermal veins, caves, and evaporite environments through precipitation or recrystallization. Calcite occurs from ancient Precambrian rocks to modern cave deposits; the specimen’s exact age cannot be determined visually.
Uses & applications
Used in cement, lime, aggregate, glass, agriculture, and chemical production; transparent crystals are collected and occasionally cut as decorative specimens. This rough piece has modest commercial value.
Geological facts
Calcite is one of Earth’s most abundant minerals and has several crystal habits, including rhombohedra, scalenohedra, fibers, and massive forms. Double refraction is visible through clear crystals.
Field identification & locations
Common worldwide, especially in limestone regions, Mexico, Iceland, the United States, and China. Confirm with its softness, rhombohedral cleavage, and acid reaction; it can be distinguished from quartz because quartz scratches calcite.
