metamorphic
Calcite-rich marble or limestone
Calcite (CaCO₃), likely recrystallized limestone (marble)
AI-generated identification · may be incorrectWhite to gray, coarse crystalline, vitreous to pearly luster, irregular fracture, and no obvious cleavage visible. Calcite has Mohs hardness 3 and commonly fizzes strongly with dilute hydrochloric acid; the specimen appears porous and locally iron-stained.
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Physical properties
White to gray, coarse crystalline, vitreous to pearly luster, irregular fracture, and no obvious cleavage visible. Calcite has Mohs hardness 3 and commonly fizzes strongly with dilute hydrochloric acid; the specimen appears porous and locally iron-stained.
Formation & geological history
Likely formed from limestone through low- to moderate-grade metamorphism, recrystallizing calcite; its precise geological age cannot be determined from the photograph. If it does not fizz, a silicate-rich rock such as altered quartzite or feldspathic gneiss is possible.
Uses & applications
Marble is used for tiles, sculpture, countertops, aggregate, and lime production; common rough pieces have little commercial value unless unusually pure, patterned, or collectible.
Geological facts
Calcite commonly shows rhombohedral cleavage and can be scratched with a steel knife. White marble may resemble quartzite, but quartzite is harder (Mohs 7) and does not react with acid.
Field identification & locations
Common worldwide in metamorphic belts and limestone regions; test an inconspicuous spot with vinegar or dilute acid and attempt a knife scratch. Estimated value: $2–$15 for a common hand specimen, potentially $20–$100 if unusually attractive or well-labeled.
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