mineral
Tumbled cream-colored mineral, likely calcite or quartz
Calcite (CaCO₃) or milky quartz (SiO₂); exact identification requires testing
AI-generated identification · may be incorrectSmall polished/tumbled, cream-white specimen with a waxy to vitreous luster and reddish-brown surface inclusion or staining. Calcite has Mohs hardness 3, rhombohedral cleavage, and effervesces in dilute acid; quartz has hardness 7, no cleavage, and does not fizz.
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Physical properties
Small polished/tumbled, cream-white specimen with a waxy to vitreous luster and reddish-brown surface inclusion or staining. Calcite has Mohs hardness 3, rhombohedral cleavage, and effervesces in dilute acid; quartz has hardness 7, no cleavage, and does not fizz.
Formation & geological history
Likely formed in a hydrothermal vein, cavity, or carbonate deposit; its geological age cannot be determined from the photograph. The rounded shape indicates human tumbling or polishing.
Uses & applications
Used mainly as a low-cost decorative or teaching specimen; calcite is important in cement and lime production, while quartz is used in glass, electronics, abrasives, and jewelry.
Geological facts
The visible red-brown area may be iron-oxide staining or a mineral inclusion. A steel nail or knife can distinguish the candidates: it scratches calcite but not quartz.
Field identification & locations
Commonly found in limestone, marble, veins, and geodes worldwide; test with hardness, streak, cleavage, and dilute hydrochloric acid rather than relying on color alone.
