Definition

Noun: A dense, dark-colored metamorphic rock consisting primarily of the minerals amphibole (especially hornblende) and plagioclase feldspar. It is formed under conditions of high temperature and pressure during the regional metamorphism of basaltic or other magnesium- and iron-rich igneous rocks.

Usage

Amphibolite is a specific term used in geology to classify a common type of metamorphic rock. It is used as both a mass noun (referring to the rock type in general) and a count noun (referring to specific specimens or outcrops).

Examples

• The mountain range's core is composed of ancient amphibolite and gneiss.
• Geologists identified several amphibolites within the metamorphic sequence.
• This amphibolite sample shows a characteristic coarse-grained, foliated texture.

Advanced Usage

• Amphibolite facies: A set of metamorphic mineral assemblages and conditions (medium to high grade) defined by the presence of rocks like amphibolite. It indicates specific ranges of pressure and temperature during rock formation.
  • The rocks were metamorphosed under conditions of the amphibolite facies.

Variants and Related Words

• Amphibole (noun): The group of dark, rock-forming silicate minerals (e.g., hornblende) that are the primary component of amphibolite.
• Metabasalt (noun): The technical term for a metamorphosed basalt, which often results in amphibolite.

Synonyms

• Hornblende schist (when strongly foliated)
• Metabasalt (specifies the protolith)

Notes on Meaning

The definition is highly specific to geology. There are no significant different common meanings, idioms, or phrasal verbs associated with this technical term. Its meaning is consistently tied to its mineral composition and metamorphic origin.

Noun

1. a metamorphic rock composed chiefly of amphibole and plagioclase