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.

 


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