Siltstone is a siliciclastic sedimentary rock composed of silt-sized grains (between 0.0625 mm and 0.00390625 mm in size; i.e., 1/16 mm to 1/256 mm in size).  These feel barely rough to the touch, whereas sandstones feel fairly rough & gritty.  Siltstones are often quartzose in composition, and they vary in color from black to gray to brown to reddish.





Home page