ARKOSE
Arkose
is a distinctive, K-feldspar-rich, siliciclastic sedimentary rock. It is usually a breccia or
sandstone. Arkoses have easily recognized clasts of pinkish- to orangish-
to salmon-colored material - that's the K-feldspar. Some arkoses have an
overall dark red coloration. Arkoses are not exclusively composed of
K-feldspar, however - there is a significant component of quartz.
Arkoses were generally deposited near their sediment
source. Source areas had fairly
significant topographic relief and had extensive exposures of granites. Large K-feldspar crystals are only
common in granites, so the source areas for arkoses had to include extensive
outcrops of felsic intrusive igneous rocks.
Arkose with
K-feldspar (pinkish-orangish) and quartz (gray) grains.