Decomposed granite, also known as DG, is granitic rock that has weathered to the point that it readily fractures into smaller pieces or chunks of weak rock. Further weathering produces rock that easily crumbles into mixtures of gravel, sand, and silt-sized particles with some clay. Eventually, the gravel-sized particles may break down to produce a mixture of silica sand or silt particles and clay.
Decomposed granite, in a crushed stone form, is used as a pavement building material. It is used on driveways, garden walkways, bocce courts and pétanque terrains,and municipal urban park and natural regional and national park 'sidewalks' and heavy-use paths. It can be installed and compacted to meet handicapped accessibility specifications and criteria, such as the ADA standards in the U.S. Different colors, in natural ranges depending on quarry source, and polymeric stabilizer add-mixtures are available.
Live Steam use
Decomposed granite has been used as ballast for live steam right of ways for decades.
Terry McGrath of the Annetta Valley & Western Railroad switched to using DG exclusively. He is happy to report that no sun kinks were seen on the extensive AV&WRR during the Texas summer heat of 2013. He attributes this to the superior gripping power of the DG ballast. He says the cost is higher than standard 3/4" ballast, but is worth it. A 10-yard load of DG, at a cost of about $1,000, will supply the AV&WRR needs for an entire year. Terry uses DG not only for ballast, but for walkways as well.