Banded calcite (likely cave-flowstone or marble fragment)

Calcite, CaCO₃; the visible bands are growth or compositional layers

Pale gray and white with curved bands and a vitreous-to-satin luster; calcite has Mohs hardness 3, trigonal crystal structure, and perfect rhombohedral cleavage. The specimen’s banding and shape are consistent with calcite, though the photo alone cannot confirm its exact origin.