Most beds are deposited essentially horizontally. The solid rock that lies beneath soil and other loose surface materials. Biotite is a black or dark brown silicate rich in iron, magnesium, potassium, aluminum, and, of course, silica. Like other micas, it forms flat book-like crystals that peal apart into individual sheets on cleavage planes. Volcanic breccia is made of volcanic rock fragments, generally blown from a volcano or eroded from it.
Fault breccia is made by breaking and grinding rocks along a fault . .
Generally white, easily scratched with knife. Most seashells are made of calcite or related minerals. This is the lime of limestone. Commonly, the magma erupts explosively as from a giant volcano and, falling back to Earth as volcanic ash, fills the caldera so formed. Limestone and dolomite are common carbonate sedimentary rocks.