Decomposed granite is a kind of

granite Granite ( ) is a coarse-grained (phanerite, phaneritic) intrusive rock, intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly coo ...

rock Rock most often refers to: * Rock (geology), a naturally occurring solid aggregate of minerals or mineraloids * Rock music, a genre of popular music Rock or Rocks may also refer to: Places United Kingdom * Rock, Caerphilly, a location in Wale ...

that is

weathered ''Weathered'' is the third studio album by American rock band Creed, released on November 20, 2001. It was the last Creed album to be released until '' Full Circle'' came out in October 2009, with Creed disbanding in June 2004. It is the only Cr ...

to the point that the parent material readily fractures into smaller pieces of weaker rock. Further weathering yields material that easily crumbles into mixtures of

gravel Gravel () is a loose aggregation of rock fragments. Gravel occurs naturally on Earth as a result of sedimentation, sedimentary and erosion, erosive geological processes; it is also produced in large quantities commercially as crushed stone. Gr ...

-sized particles known as grus that further may break down to produce a mixture of clay and silica sand or silt particles. Different specific granite types have differing propensities to weather, and so differing likelihoods of producing decomposed granite. It has practical uses that include its incorporation into roadway and

driveway A driveway (also called ''drive'' in UK English) is a private road for local access to one or a small group of structures owned and maintained by an individual or group. Driveways rarely have traffic lights, but some may if they handle heavy ...

paving materials, residential gardening materials in arid environments, as well as various types of

walkway In American English, walkway is a composite or umbrella term for all engineered surfaces or structures which support the use of trails. '' The New Oxford American Dictionary'' also defines a walkway as "a passage or path for walking along, esp. ...

s and heavy-use paths in

park A park is an area of natural, semi-natural or planted space set aside for human enjoyment and recreation or for the protection of wildlife or natural habitats. Urban parks are urban green space, green spaces set aside for recreation inside t ...

s. Different colors of decomposed granite are available, deriving from the natural range of granite colors from different quarry sources, and admixture of other natural and synthetic materials can extend the range of decomposed granite properties.

Definition and composition

Decomposed granite is

granitic A granitoid is a broad term referring to a diverse group of coarse-grained igneous rocks that are widely distributed across the globe, covering a significant portion of the Earth's exposed surface and constituting a large part of the continental ...

origin that has

to the point that it readily fractures into smaller pieces of weak rock. Further weathering produces rock that easily crumbles into mixtures of

-sized particles,

sand Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is usually defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a textural ...

, and

silt Silt is granular material of a size between sand and clay and composed mostly of broken grains of quartz. Silt may occur as a soil (often mixed with sand or clay) or as sediment mixed in suspension (chemistry), suspension with water. Silt usually ...

-sized particles with some

clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolinite, ). Most pure clay minerals are white or light-coloured, but natural clays show a variety of colours from impuriti ...

. Eventually, the gravel may break down to produce a mixture of silica sand, silt particles, and clay. Different specific granite types have differing propensities to weather, and so differing likelihoods of producing decomposed granite. The parent

material is a common type of

igneous rock Igneous rock ( ), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rocks are formed through the cooling and solidification of magma or lava. The magma can be derived from partial ...

that is granular, with its grains large enough to be distinguished with the unaided eye (i.e., it is

phaneritic A phanerite is an igneous rock whose microstructure is made up of crystals large enough to be distinguished with the unaided human eye. In contrast, the crystals in an aphanitic rock are too fine-grained to be identifiable. Phaneritic texture fo ...

in texture); it is composed of

plagioclase feldspar Plagioclase ( ) is a series of tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a continuous solid solution series, more pr ...

orthoclase feldspar Orthoclase, or orthoclase feldspar (endmember formula K Al Si3 O8), is an important tectosilicate mineral which forms igneous rock. The name is from the Ancient Greek for "straight fracture", because its two cleavage planes are at right angles t ...

quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The Atom, atoms are linked in a continuous framework of SiO4 silicon–oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tet ...

mica Micas ( ) are a group of silicate minerals whose outstanding physical characteristic is that individual mica crystals can easily be split into fragile elastic plates. This characteristic is described as ''perfect basal cleavage''. Mica is co ...

, and possibly other minerals. The chemical transformation of

feldspar Feldspar ( ; sometimes spelled felspar) is a group of rock-forming aluminium tectosilicate minerals, also containing other cations such as sodium, calcium, potassium, or barium. The most common members of the feldspar group are the ''plagiocl ...

, one of the primary constituents of

, into the clay mineral

kaolin Kaolinite ( ; also called kaolin) is a clay mineral, with the chemical composition Al2 Si2 O5( OH)4. It is a layered silicate mineral, with one tetrahedral sheet of silica () linked through oxygen atoms to one octahedral sheet of alumina (). ...

is one of the important weathering processes.Mitchell, J.K., and Soga, K. (2005) Fundamentals of soil behavior, Third edition, John Wiley and Sons, Inc., , pages 200-204. The presence of clay allows water to seep in and further weaken the rock allowing it to fracture or crumble into smaller particles, where, ultimately, the grains of

silica Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , commonly found in nature as quartz. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and abundant f ...

produced from the granite are relatively resistant to weathering, and may remain almost unaltered.

Uses

Decomposed granite, as a

crushed stone Crushed stone or angular rock is a form of construction aggregate, typically produced by mining a suitable rock deposit and breaking the removed rock down to the desired size using crushers. It is distinct from naturally occurring gravel, whi ...

form, is used as a pavement

building material Building material is material used for construction. Many naturally occurring substances, such as clay, rocks, sand, wood, and even twigs and leaves, have been used to construct buildings and other structures, like bridges. Apart from natur ...

. It is used on

garden A garden is a planned space, usually outdoors, set aside for the cultivation, display, and enjoyment of plants and other forms of nature. The single feature identifying even the wildest wild garden is ''control''. The garden can incorporate bot ...

bocce (, or , ), sometimes anglicized as bocce ball, bocci, or boccie, is a ball sport belonging to the boules family. Developed into its present form in Italy, it is closely related to English bowls and French , with a common ancestry from anc ...

courts and

pétanque Pétanque (, ; ; ) is a sport that falls into the category of boules sports (along with Raffa (boules), raffa, bocce, boule lyonnaise, Bowls, lawn bowls, and Crown green bowls, crown green bowling). In these sports, players or teams play thei ...

terrains, and urban,

regional In geography, regions, otherwise referred to as areas, zones, lands or territories, are portions of the Earth's surface that are broadly divided by physical characteristics (physical geography), human impact characteristics (human geography), and ...

, and

national park A national park is a nature park designated for conservation (ethic), conservation purposes because of unparalleled national natural, historic, or cultural significance. It is an area of natural, semi-natural, or developed land that is protecte ...

walkways and heavy-use paths. DG can be installed and compacted to meet handicapped accessibility specifications and criteria, such as the ADA standards in the U.S. Different colors are available based on the various natural ranges available from different quarry sources, and polymeric stabilizers and other additives can be included to change the properties of the natural material. Decomposed granite is also sometimes used as a component of soil mixtures for cultivating

bonsai Bonsai (; , ) is the Japanese art of Horticulture, growing and shaping miniature trees in containers, with a long documented history of influences and native Japanese development over a thousand years, and with unique aesthetics, cultural hist ...

References

{{reflist Granite Building stone Pavements Road construction Earthworks (engineering) Natural materials Stone (material)

Definition and composition

Uses

See also

References