A sample contains 60 % Plagioclase Feldspar and a medium amount of silica. What would you call it?
A) an intermediate igneous rock
B) a mafic igneous rock
C) an ultramafic igneous rock
D) a felsic igneous rock

Question

Quizplus · Accepted Answer

The high percentage of plagioclase feldspar suggests that the rock is not mafic or ultramafic, as those types of rocks have lower percentages of this mineral. The medium amount of silica also rules out felsic rocks, which have a higher percentage of silica. Therefore, the most likely classification for this rock is intermediate.

A Sample Contains 60 % Plagioclase Feldspar and a Medium