Limestone River Pebble

Hardness 3 (Mohs scale), dull luster, fine-grained texture, light gray to beige color with some weathering rinds, reacts with dilute hydrochloric acid.

Formed through the accumulation of marine organisms and chemical precipitation in ancient seas, likely during the Mesozoic era given the French Alps/Vercors region (Drôme). It has been rounded and smoothed by fluvial (river) transport.

Limestone is used widely in building construction, cement production, and as an industrial flux; smoothed pebbles like this are often used in decorative landscaping.

The coordinates provided (44.7°N, 5.2°E) place this in the Drôme department of France, a region famous for its massive Jurassic and Cretaceous limestone massifs like the Vercors. The green tint on the edges is likely organic algae growth from a moist environment.

Identify by its light color, smooth water-worn surface, and softness (it can be scratched by a steel blade). Common in riverbeds and scree slopes throughout Southeast France.