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Igneous or metamorphic rock composed largely or dominantly of amphibole minerals. For igneous rocks, the term hornblendite is usually used and is more restrictive; hornblende is the most common amphibole. Metamorphic amphibolites are more widespread and variable than igneous ones. Typically, they are medium- to coarse-grained and are composed of hornblende and plagioclase. Basic igneous rocks such as basalts and gabbros (seeacid and basic rocks) can be the parent rocks of amphibolite.
This entry comes from Encyclopædia Britannica Concise. For the full entry on amphibolite, visit Britannica.com.