> Types of pebbles <
1. Marble pebbles are rounded fragments of metamorphic limestone rock, polished naturally or mechanically by abrasion. Composed primarily of calcite, they have a moderate hardness (3 to 4 on the Mohs scale) and a lustrous appearance, with varying hues depending on mineral impurities.
2. River pebbles are alluvial elements of sedimentary origin, formed by the mechanical erosion of rocks as they are transported in waterways. Their rounded shape and smooth surface result from prolonged rolling, and their composition varies depending on the local rocks (quartz, granite, schist), with a generally higher hardness than limestone pebbles.
3. Quartz gravel pebbles are rounded fragments resulting from the degradation of silica-rich rocks, primarily composed of quartz, a very hard mineral (7 on the Mohs scale). Their rounded shape results from fluvial or glacial transport, and their translucent to milky white, sometimes glistening, appearance testifies to their high resistance to chemical and mechanical weathering.
4. Rounded pebbles are rock fragments rounded by the prolonged mechanical action of water or glaciers, which polish them over time. Their composition is highly variable (limestone, quartz, granite, etc.), but their smooth, regular shape testifies to long transport and natural wear.
5. Sandstone pebbles come from sedimentary rocks composed mainly of quartz grains bound by a natural cement (siliceous, calcareous, or clayey). Relatively hard (hardness between 6 and 7 on the Mohs scale), they have a granular texture and a color ranging from beige to red depending on the nature of the cement and the iron oxides present.
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