A nonfoliated metamorphic rock consisting principally of hornblende and plagioclase is called

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Study for the ASBOG Fundamentals of Geology exam. Access flashcards, multiple-choice questions, and understand key geologic principles. Prepare confidently for your exam!

Multiple Choice

A nonfoliated metamorphic rock consisting principally of hornblende and plagioclase is called

Explanation:
This is amphibolite. It’s a mafic, metamorphic rock whose defining minerals are hornblende (an amphibole) and plagioclase feldspar. The texture is nonfoliated, meaning there isn’t a layered or lineated mineral alignment, which helps distinguish it from foliated mafic rocks like schists or gneisses. Marble would be dominated by calcite/dolomite; quartzite is mainly quartz; hornfels is a nonfoliated rock formed by contact metamorphism but its mineralogy isn’t specifically hornblende plus plagioclase. So the combination of hornblende and plagioclase with a nonfoliated texture best identifies amphibolite.

This is amphibolite. It’s a mafic, metamorphic rock whose defining minerals are hornblende (an amphibole) and plagioclase feldspar. The texture is nonfoliated, meaning there isn’t a layered or lineated mineral alignment, which helps distinguish it from foliated mafic rocks like schists or gneisses. Marble would be dominated by calcite/dolomite; quartzite is mainly quartz; hornfels is a nonfoliated rock formed by contact metamorphism but its mineralogy isn’t specifically hornblende plus plagioclase. So the combination of hornblende and plagioclase with a nonfoliated texture best identifies amphibolite.

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