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Porphyritic identification and geology

An igneous rock texture characterized by large crystals phenocrysts set in a finer-grained groundmass, indicating a two-stage cooling history. The phenocrysts grew slowly during an initial period of slow cooling at depth, then the remaining magma cooled rapidly either by erupting at the surface or being emplaced at a shallow level , producing the fine-grained or glassy matrix. Field: petrology. Example: Porphyry copper deposits form in porphyritic intrusions where copper sulfides were precipitated from hydrothermal fluids emanating from the crystallizing magma—the Bingham Canyon mine in Utah is a classic example.. Related terms: Phenocryst, Groundmass, Aphanitic, Phaneritic.

Sources, scope & corrections

These authoritative resources support category-level nomenclature, terminology, identification methods, and safety. When a specimen-specific safety warning appears, the public-health source listed here directly supports that precaution. They are not line-by-line citations for every other property on this entry, and natural specimens vary.

Editorial owner
GeoMiner
Last updated
2026-03-30T15:19:42.055955+00:00
Review status
Published; not independently peer-reviewed
  • USGS Thesaurus — U.S. Geological Survey. Controlled earth-science terminology used to describe USGS information resources.
  • Glossary of Geologic Terms — U.S. National Park Service. Geologic definitions prepared by the NPS Geologic Resources Inventory.

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Common questions

What does Porphyritic mean in geology?
An igneous rock texture characterized by large crystals phenocrysts set in a finer-grained groundmass, indicating a two-stage cooling history. The phenocrysts grew slowly during an initial period of slow cooling at depth, then the remaining magma cooled rapidly either by erupting at the surface or being emplaced at a shallow level , producing the fine-grained or glassy matrix.
What is an example of Porphyritic?
Porphyry copper deposits form in porphyritic intrusions where copper sulfides were precipitated from hydrothermal fluids emanating from the crystallizing magma—the Bingham Canyon mine in Utah is a classic example.
Which earth-science field uses the term Porphyritic?
Porphyritic is used in petrology.
Which terms are related to Porphyritic?
Related terms in this reference are Phenocryst, Groundmass, Aphanitic, Phaneritic.

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