What is Gravel?
[[File:Gravel on a beach in Thirasia, Santorini, Greece.jpg|thumb|right|230px|Gravel (largest fragment in this photo is about 4 cm).]] [[File:Gravel near White Down Cross - geograph.org.uk - 1765878.jpg|thumb|right|230px|Gravel piles at a roadside, waiting for the road repair gang]] '''Gravel''' is small, loose, [[Rock (geology)|rock]] [[particle]]s. It is any loose rock that is larger than 2 mm (0.079 in) in its smallest [[dimension]] (about 1/12 of an inch) and no more than 64 mm (2.5 in). Small gravel is composed of [[granule]]s (>2 to 4 mm/0.079 to 0.16 in). Large gravel is called [[pebble]]s (>4 to 64 mm/0.16 to 2.5 in). Particles smaller than gravel are [[sand]], larger particles are [[cobble]]s. Gravel and sand are used for road surfaces, and for [[cement]] and [[Tarmac]]. Mixtures of gravel and sand mixed with various crushed material, are known as ''aggregate'' in the trade. This is used for [[drain]]age in the basement of roads, and other purposes. Mixture of stones and resin is also used to pave footpaths, driveways, etc. This mixture is known as Resin Bonded Gravel.<ref>{{Cite web|last=|first=|date=|title=Resin Bonded Gravel|url=https://resinbondedgravel.uk/|archive-url=|archive-date=|access-date=2020-10-29|website=Resin Bonded Gravel|language=en-GB}}</ref><ref>{{Cite web|title=Resin Bonded Gravel|url=https://www.resinbondedgravel.org.uk/|access-date=2020-11-16|website=www.resinbondedgravel.org.uk}}</ref> == Origin == Natural gravel comes from ancient [[beach]]es which have not consolidated (turned into solid rock). In effect, beaches from (for instance) the [[Jurassic]] are dug up in [[Quarry|quarries]]. The material is then [[wikt:sort|sifted]] into size categories. The gravel and sand is then sold on to [[engineering]] companies. Most natural sand and gravel is [[silica]], SiO<sub>2</sub>, in its [[chemistry]]. This is very hard-wearing. However, if the material is originally in hard rock form, then it is first [[wikt:crush|crushed]]. This enables the industry to offer other materials such a