Carved limestone architectural fragment

Light gray, porous, fine- to medium-grained, with earthy/matte luster and irregular cavities; calcite hardness is Mohs 3, with weak cleavage and specific gravity about 2.7. Effervesces visibly with dilute hydrochloric acid or vinegar if unweathered.

Formed from accumulated carbonate sediment or biological debris that lithified into limestone, commonly during the Paleozoic–Cenozoic; this piece has been quarried and human-carved, likely as masonry or an architectural/artifact fragment.

Used extensively for building stone, sculpture, lime and cement manufacture, and aggregate; this specimen is primarily archaeological, architectural, or museum-display material rather than jewelry stone.

The recessed face appears carved or inserted and is not a natural mineral feature, while the surrounding stone shows weathering and tool-related cavities. Limestone is especially vulnerable to acidic rain and dissolution.

Identify by its pale gray color, softness, carbonate reaction, and powdery texture; distinguish it from concrete by the absence of manufactured cement paste and uniform aggregate. Common worldwide, especially in marine sedimentary basins; value is typically $20–$200 for an ordinary fragment, potentially much higher if authenticated as an archaeological or historically significant artifact.