Microlite (petrographic)
A minute recognisable crystal in fine-grained or glassy rock, often a feldspar lath, observable in thin section.
Language and route: English scientific word from Greek-derived elements; mineral-name homonym is separate. English scientific word from Greek-derived elements; mineral-name homonym is separate
Literal gloss: small stone / very small crystal
The name and its history
Microscopical petrographic term; first use not verified · Microscopical petrographic term; first use not verified
- What does the word literally mean?
- Immediate route: English scientific word from Greek-derived elements; mineral-name homonym is separate. Linguistic gloss: ‘small stone / very small crystal’. This gloss describes language, not a demonstrated early geological theory.
- What did the original author mean?
- Nineteenth-century microscopical work supplied terms for crystals too small to classify in hand specimen but meaningful in lava groundmass.
- Why was the name needed?
- Crystallites, microlites and larger phenocrysts had to be separated when interpreting incomplete volcanic crystallisation.
- What evidence supported the original concept?
- Optically distinguishable microcrystals and their lath, needle or branching habits in groundmass; some incipient crystallites resist optical identification.
- How has geology changed the concept?
- Textural microlite must not be confused with the mineralogical historical microlite name (pyrochlore-supergroup nomenclature); grain-size boundaries vary by observer.
Further historical context
Nineteenth-century microscopical work supplied terms for crystals too small to classify in hand specimen but meaningful in lava groundmass.
Crystallites, microlites and larger phenocrysts had to be separated when interpreting incomplete volcanic crystallisation.
Optically distinguishable microcrystals and their lath, needle or branching habits in groundmass; some incipient crystallites resist optical identification.
Textural microlite must not be confused with the mineralogical historical microlite name (pyrochlore-supergroup nomenclature); grain-size boundaries vary by observer.
Editorial qualification
Microlite is also a historically separate mineralogical word; no false species equation.
Related names
Sources
- Geological Survey of India, Rock Texture Atlas — Photomicrographs and modern texture definitions
- International Ocean Discovery Program, Expedition 360 methods — Operational definitions for igneous groundmass, flow and inclusion textures