Gravel

Gravel occurs naturally on Earth as a result of sedimentary and erosive geological processes; it is also produced in large quantities commercially as crushed stone.

Naturally occurring porous gravel deposits have a high hydraulic conductivity, making them important aquifers.

Colloquially, the term gravel is often used to describe a mixture of different size pieces of stone mixed with sand and possibly some clay.

Many geologists define gravel simply as loose rounded rock particles over 2 mm (0.079 in) in diameter, without specifying an upper size limit.

[5][6][7][8] Gravel is sometimes distinguished from rubble, which is loose rock particles in the same size range but angular in shape.

Quartz is the most common mineral found in gravel, as it is hard, chemically inert, and lacks cleavage planes along which the rock easily splits.

Exceptions include quartz veins, pegmatites, deep intrusions, and high-grade metamorphic rock.

Types of gravel include: In locales where gravelly soil is predominant, plant life is generally more sparse.

[18] These include conglomerates of the Triassic basins of eastern North America and the New Red Sandstone of south Devon.