Glomeroporphyritic
A porphyritic texture in which phenocrysts form conspicuous aggregates or crystal clots (glomerocrysts).
Language and route: English petrographic coinage combining Latin glomero- and porphyritic. English petrographic coinage combining Latin glomero- and porphyritic
Literal gloss: clustered porphyritic crystals
The name and its history
J. W. Judd, 1886, according to Holmes and later discussions · J. W. Judd, 1886, according to Holmes and later discussions
- What does the word literally mean?
- Immediate route: English petrographic coinage combining Latin glomero- and porphyritic. Linguistic gloss: ‘clustered porphyritic crystals’. This gloss describes language, not a demonstrated early geological theory.
- What did the original author mean?
- J. W. Judd used glomeroporphyritic in his 1886 discussion of Tertiary Scottish and Irish igneous rocks. Later writers disputed whether aggregates must be monomineralic.
- Why was the name needed?
- One needed to describe clotted groups of conspicuous crystals separately from individual phenocrysts in rocks showing multiple crystallisation textures.
- What evidence supported the original concept?
- Petrographic observations of crystal aggregates in gabbros, dolerites and basalts, documented in Judd 1886 p. 71 according to Holmes’s retrospective nomenclature register.
- How has geology changed the concept?
- Modern workers allow clots of one or several minerals and test how they formed (growth, aggregation or inherited fragments); shape alone does not prove synneusis or settling.
Further historical context
J. W. Judd used glomeroporphyritic in his 1886 discussion of Tertiary Scottish and Irish igneous rocks. Later writers disputed whether aggregates must be monomineralic.
One needed to describe clotted groups of conspicuous crystals separately from individual phenocrysts in rocks showing multiple crystallisation textures.
Petrographic observations of crystal aggregates in gabbros, dolerites and basalts, documented in Judd 1886 p. 71 according to Holmes’s retrospective nomenclature register.
Modern workers allow clots of one or several minerals and test how they formed (growth, aggregation or inherited fragments); shape alone does not prove synneusis or settling.
Editorial qualification
Judd (1886) p. 71 was identified from later sources; inspect facsimile before treating his exact wording as verified.
Related names
Phenocryst · Porphyritic · Synneusis · Poikilitic · Basalt
Sources
- Geological Survey of India, Rock Texture Atlas — Photomicrographs and modern texture definitions
- International Ocean Discovery Program, Expedition 350 methods — Description criteria for volcanic texture and vesicle proportions
- Judd (1886), Scottish and Irish Tertiary igneous rocks — Original identified, p. 71 reported in secondary register; original passage not independently transcribed
- Holmes, Nomenclature of Petrology, glomeroporphyritic — Retrospective attribution to Judd (1886), p. 71, not independent original-text verification