Foliated Coarse grain

You have now identified a coarse grained, foliated metamorphic rock. To complete the identification process you must further classify the degree of foliation. Use the Table below to determine whether the rock you are identifying exhibits schistosity or gneissic foliation; direction on how to name the metamorphic rock are in the last column.

Texture
Example
Name
Parent Rock
Schistosity
  • a scaly layering of large (visible) crystals of platy minerals such as amphibole, micas, and chlorite
  • product of intermediate to high grade metamorphism

Schist

Modify the name with constiuent minerals in order of abundance

Example Name: Hornblend Schist

Mudstone or Shale
 
Gneissic
  • Alternating layers of dark and light medium to coarse grained mineral crystals
  • Indicative of high grade metamorphism

Gneiss

Modify the name with constiuent minerals in order of abundance

Example Name: K-Spar Hornblend Gniess

Granite




©2006 Sean Tvelia