hornblendite

rock

Written by

The Information Architects of Encyclopaedia Britannica

Last updated

June 29, 2026

Quick Summary

Hornblendite is a granular igneous rock composed almost entirely of the mineral hornblende. Hornblende is a calcium-rich amphibole mineral with a monoclinic crystal structure. Its generalized chemical formula is (Ca,Na)₂(Mg,Fe,Al)₅(Al,Si)₈O₂₂(OH)₂. Hornblende is found in both metamorphic and igneous rocks, and metamorphic rocks rich in hornblende are called amphibolites. Hornblendite itself is an igneous rock, meaning it forms from the cooling and solidification of molten rock.12

Summary created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

3 Britannica Sources

Ask Britannica AI about this topic

Britannica doesn't have a full article on this topic, so we've curated a list of our relevant coverage.

amphibolite
In igneous rocks, the term hornblendite is more common and restrictive; hornblende is the most common amphibole and is typical of such rocks. Hornblendite is an ultramafic rock (dominantly dark minerals). True hornblendites contain little other than amphibole and are probably derived from the alteration of pyroxene and olivine.
Read More
In igneous rocks, the term hornblendite is more common and restrictive; hornblende is the most common amphibole and is typical of such rocks. Hornblendite is an ultramafic rock (dominantly dark minerals). True hornblendites contain little other than amphibole and are probably derived from the alteration of pyroxene and olivine.
Read More