Sand and Gravel

Sand and gravel deposits found on beaches or in rivers and streams, are mostly quartz (silicon dioxide, SiO2) grains. Weathering of rocks such as granite forms these quartz grains. In the process of weathering, the softer, weaker minerals in granite (such as feldspar) are weathered away. The more resistant quartz eventually is ground down in size, but does not break down chemically. In time, these quartz grains accumulate in rivers, streams, deltas and on beaches.

Industrial sand mining methods are contingent on deposit type. Unconsolidated deposits are mined using front-end loaders, scrapers, or bulldozers. Material is dug, excavated, and pushed to a central point. The ore-grade material is then loaded onto a truck using standard earth-moving equipment, where it then reports to a stockpile or a processing plant.

A hydraulic dredge uses a suction pipe to excavate the sand, which is pumped through a pipeline to surge piles or directly to a processing plant. The channel or tailings deposit is excavated and placed in a stockpile. The ore-grade material is loaded into haul trucks for transportation to a processing plant.

Sand and gravel are used for road construction, for mixing with asphalt, as construction fill, and in the production of construction materials like concrete blocks, bricks, and pipes. It is also used to make roofing shingles, used on icy roads in the winter, for railroad ballast, and water filtration.

Industrial sand and gravel is used to make glass, as foundry sand and as abrasive sand.

For some applications, it is the silica content (quartz) of sand that makes it so valuable. The silica itself is needed to make products such as glass. In addition, the physical properties of sand, particularly its abrasive property, make it useful for traction on icy roadways and railroads, and for sandblasting.