Decomposed granite

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

While decomposed granite works well for walkways and paths, it has been found to be less than sufficient when used as ballast on 1/8 scale track. This was discovered after extensive use on the Annetta Valley & Western Railroad. Under the direction of Charlie Linck the railroad has switched to using 3/4 inch crushed limestone. The large diameter rock is rough so it "locks" into place, and helps keep the ties high and dry.

References

• "Decomposed granite", Wikipedia
• Graniterock, supplier of full-size DG ballast