Amphibolite
Metamorphic rock dominated by amphibole and plagioclase, commonly with a mafic protolith, but not defined solely by one grade.
Language and route: Scientific French/German or English formation from amphibole (the mineral group) + -ite; exact first language route unverified. Scientific French/German or English formation from amphibole (the mineral group) + -ite; exact first language route unverified
Literal gloss: amphibole-bearing rock
The name and its history
First individual geological coiner not established · Original naming act not securely page-verified
- What does the word literally mean?
- Immediate linguistic route: Scientific French/German or English formation from amphibole (the mineral group) + -ite; exact first language route unverified. Literal or inherited gloss: ‘amphibole-bearing rock’. An attested linguistic component is not by itself evidence of a historical scientist’s reason for naming this rock.
- What did the original author mean?
- Petrographers separated amphibole-bearing crystalline rocks by their constituent minerals before metamorphic assemblages could be linked quantitatively to pressure and temperature.
- Why was the name needed?
- Field and laboratory schemes needed to distinguish amphibole-rich rocks from pyroxene granulites and hornblende-rich igneous rocks.
- What evidence supported the original concept?
- Modal amphibole and plagioclase, metamorphic fabric and microstructures established the lithological description; facies arguments rely on assemblages and bulk composition.
- How has geology changed the concept?
- The IUGS specific name amphibolite remains lithological, whereas amphibolite facies describes P–T conditions inferred from suitable mineral assemblages in rocks of specified composition.
Further historical context
Petrographers separated amphibole-bearing crystalline rocks by their constituent minerals before metamorphic assemblages could be linked quantitatively to pressure and temperature.
Field and laboratory schemes needed to distinguish amphibole-rich rocks from pyroxene granulites and hornblende-rich igneous rocks.
Modal amphibole and plagioclase, metamorphic fabric and microstructures established the lithological description; facies arguments rely on assemblages and bulk composition.
The IUGS specific name amphibolite remains lithological, whereas amphibolite facies describes P–T conditions inferred from suitable mineral assemblages in rocks of specified composition.
Editorial qualification
Do not equate an early recorded description with a formal first coining; exact priority and historical wording remain unverified.
Related names
Amphibole · Granulite · Blueschist · Greenschist · Nematoblastic · Facies
Sources
- IUGS SCMR, Amphibolite and Granulite recommendations — different meanings of granulite and compositional amphibolite criteria
- IUGS SCMR, Schmid et al., How to Name a Metamorphic Rock (2004 web edition) — professional nomenclature recommendation; relevant text checked, not original historical coining
- Eskola, The Mineral Facies of Rocks (1920), Norsk Geologisk Tidsskrift, 6:143–194 — identified original facies research publication, pages not independently checked