3.7 Notes
How are metamorphic rocks classified?
Objective: Explain the difference between foliated and non-foliated metamorphic
rocks.
The texture of a metamorphic rock with minerals arranged in bands is called
foliated.
The texture of a metamorphic rock that DOES NOT has its minerals arranged in
bands is Nonfoliated.
Petrologists classify metamorphic rocks by its texture: foliated or Nonfoliated.
How are metamorphic rocks grouped?
Foliated rocks break along their mineral crystal bands.
Foliated metamorphic rocks form when existing rocks are placed under great heat
and pressure. Minerals in the rocks melt into bands.
Granite

heat and pressure

Gneiss
Nonfoliated metamorphic rocks do NOT break in layers.
Marble and quartzite are non-foliated metamorphic rocks. Marble is formed from
limestone and contains large mineral crystals of calcite.
Sandstone

heat and pressure
 Quartzite
Quartzite has large crystals of quartz.
Which metamorphic rock has large crystals of quartz formed from sand – marble
or quartzite?