A coarse-grained weakly foliated metamorphic rock composed of plagioclase feldspar and hornblende (an amphibole) is classified as a(n)
A) marble.
B) greenstone.
C) amphibolite.
D) hornfels.

Question

Quizplus · Accepted Answer

The given description fits the characteristics of amphibolite, which is a coarse-grained metamorphic rock composed of plagioclase feldspar and hornblende. Marble is composed of calcite or dolomite and does not contain hornblende. Greenstone is a term used for various types of altered basaltic rocks and may not necessarily contain plagioclase feldspar. Hornfels is a non-foliated metamorphic rock that does not contain any particular mineral composition.

A Coarse-Grained Weakly Foliated Metamorphic Rock Composed of Plagioclase Feldspar