Decomposed granite 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 granite material is a common type of igneous rock that is granular, with its grains large enough to be distinguished with the unaided eye (i.e., it is phaneritic in texture); it is composed of plagioclase feldspar, orthoclase feldspar, quartz, mica, and possibly other minerals. The chemical transformation of feldspar, one of the primary constituents of granite, into the clay mineral kaolin is one of the important weathering processes. The presence of clay allows water
Granite Dells old Prescott & Eastern Railroad through the eastern Granite Dells. Both are rail trail conversions. The precambrian Dells' granite has been dated at 1.4 billion years old. Its pluton was intruded at a depth of around one or two miles (1.6 to 3.2 km). These cover rocks have since been eroded away. Weathering along joints produced the rounded boulders and other unusual rock formations that characterize the Granite Dells. This process is called spheroidal weathering, and is common in granitic terrains. The Dells' granite has an unusually high uranium content, and thus homes built over the granite should be checked