Eclogite
High-pressure metamorphic rock typically containing garnet and omphacitic clinopyroxene, usually without primary plagioclase.
Language and route: Scientific French éclogite coined from Ancient Greek ἐκλογή (eklogḗ), choice, selection. Scientific French éclogite coined from Ancient Greek ἐκλογή (eklogḗ), choice, selection
Literal gloss: chosen rock
The name and its history
René-Just Haüy (historical attribution via conference research history) · 1822, Traité de minéralogie (original printed page not independently checked)
- What does the word literally mean?
- Immediate linguistic route: Scientific French éclogite coined from Ancient Greek ἐκλογή (eklogḗ), choice, selection. Literal or inherited gloss: ‘chosen 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?
- Haüy named an unusually distinctive rock assemblage in 1822; a descriptive account by de Saussure preceded this, and neither original observation was a modern subduction hypothesis.
- Why was the name needed?
- The naming made a striking garnet–green-pyroxene assemblage distinguishable from other crystalline rocks that looked superficially similar.
- What evidence supported the original concept?
- Recognisable garnet and green pyroxene in Alpine specimens first supported distinction; Becke 1903 and Eskola 1920 later used mineral paragenesis/volume arguments to infer high pressure.
- How has geology changed the concept?
- Experiment, thermodynamics and coesite discoveries made some eclogites records of deep subduction; eclogite the rock is not the same thing as any rock in eclogite facies.
Further historical context
Haüy named an unusually distinctive rock assemblage in 1822; a descriptive account by de Saussure preceded this, and neither original observation was a modern subduction hypothesis.
The naming made a striking garnet–green-pyroxene assemblage distinguishable from other crystalline rocks that looked superficially similar.
Recognisable garnet and green pyroxene in Alpine specimens first supported distinction; Becke 1903 and Eskola 1920 later used mineral paragenesis/volume arguments to infer high pressure.
Experiment, thermodynamics and coesite discoveries made some eclogites records of deep subduction; eclogite the rock is not the same thing as any rock in eclogite facies.
Editorial qualification
Do not equate an early recorded description with a formal first coining; exact priority and historical wording remain unverified.
Related names
Granulite · Amphibolite · Blueschist · Facies
Sources
- International Eclogite Conference, History of Eclogite — secondary history identifies Haüy 1822 and antecedent de Saussure description
- Eclogites and their geodynamic interpretation: a history (2001) — peer-reviewed historical synthesis: 1903 Becke, 1920 Eskola, later experiments and UHP
- IUGS SCMR, High pressure/temperature metamorphic rocks — guidance on eclogite and blueschist rock-name versus facies-name distinction
- Eskola, The Mineral Facies of Rocks (1920), Norsk Geologisk Tidsskrift, 6:143–194 — identified original facies research publication, pages not independently checked