metamorphic
Marble (Polished Sphere / Clay Marble)
Metamorphosed Limestone (principally Calcite, CaCO3)
AI-generated identification · may be incorrectHardness 3 on Mohs scale; white to pale gray with dull to waxy luster; reacts with dilute HCl; specific gravity ~2.7.
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Physical properties
Hardness 3 on Mohs scale; white to pale gray with dull to waxy luster; reacts with dilute HCl; specific gravity ~2.7.
Formation & geological history
Formed via regional or contact metamorphism of carbonate sedimentary rocks like limestone or dolostone, subsequently shaped into a sphere.
Uses & applications
Used historically as game marbles, slingshot ammunition, or decorative spheres and beads.
Geological facts
Antique hand-ground stone or fired clay marbles were commonly used in folk games across Europe, the Middle East, and North America before glass marbles became dominant.
Field identification & locations
Identified by its spherical form, soft calcite-like feel or fine-grained texture, and mild reaction to acid tests.
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