FORMATION OF METAMORPHIC ROCKS
Metamorphic rocks are either easy to identify or
very difficult. Some textures or appearances, like foliation, are
unique to metamorphic rocks. Foliation comes from the Latin meaning
leafy. The texture is platy because it contains minerals like mica.
However some nonfoliated textures like granoblastic or minerals
that are large grained are difficult to distinguish from chemical
sedimentary or plutonic igneous rocks. These rocks do not have a
On the identification chart we separate the rocks
by texture and refer to them as foliated or nonfoliated. Both groups are
further subdivided by coarse and fine grained, depending on the size of
the minerals. Mineral groups that are found within each rock can also
help to identify the type of metamorphic rock.
Mica (bluish) is aligned in a foliated texture
in this mica schist (thin section)
Granoblastic texture of quartzite (thin section)