SEDIMENTARY AND METAMORPHIC ROCKS 101 
pressure, because this is the plane of least resistance. 
Therefore slate splits in this direction, taking advantage 
of the many cleavage planes of the newly formed 
micaceous mineral. 
Fig. 45. 
Mica schist. Schistose structure parallel to the surface. White particles are 
mica flakes which reflect the light from their smooth cleavage faces. 
A little more metamorphism of the slate rock would 
develop other minerals, and soon it would become 
entirely different in character, a schist (Fig. 45), in 
which the various minerals are arranged in bands, and 
in which there is also a cleavage, though less marked 
as 
