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
Bohus granite the Lysekil Line. In Norway Iddefjord granite has been a relatively common rock in architecture, further many of the renown statues of Frogner Park in Oslo are made of Iddefjord granite. Iddefjord granite is the official county rock of Østfold in Norway. Geologically the Bohus is a monzogranite, a subtype of granite. Besides the main minerals plagioclase, K-feldspar and quartz the Bohus granites contain lesser amounts of magnetite, apatite, zircon, titanite, garnet and monazite. In restricted areas alteration of the original rock has added prehnite, calcite and chlorite to the mineral assemblage. The texture of the granites varies from fine