CHAPTER V 
SEDIMENTARY AND METAMORPHIC ROCKS 
STRATIFIED OR SEDIMENTARY Rocks 
Terms used. —The term sedimentary is not satis- 
factory, for it assumes that the rock is actually a sedi- 
ment; and in this group we must include some kinds 
which are not really sedimentary in origin. Sometimes 
the members of this group are called stratified, because 
they occur in layers or strata, but there are certain 
members of which this is not true. Many of the so- 
called sedimentary beds are composed of fragments 
of other rocks, and these are often called fragmental 
or clastic. Most of them are formed in water, and 
these might be called aqueous. Rather than inyent 
terms, we will use the names sedimentary and stratified, 
with the understanding that some of the members in- 
cluded are neither true sediments nor stratified. 
Origin of the Rocks. — As is stated elsewhere (see 
Chapter VI.), when exposed at the surface, minerals are 
subjected to destruction. The beating of waves on 
the seashore, the grinding of pebbles in the bottom 
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