porphyry

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Eight labeled rock samples are shown, including black glassy obsidian, speckled porphyry, striped calico sandstone, shell-filled coquina limestone, coarse breccia, layered banded gneiss, pale green fibrous talc schist, and greenish serpentine.

porphyry

geological feature

Also known as: porphyritic texture

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July 1, 2026

Quick Summary

porphyry — porphyry Porphyry.

Porphyry is a type of igneous rock characterized by large crystals, called phenocrysts, embedded within a finer-grained groundmass. These rocks often have a dark red or purple hue due to the feldspar crystals and groundmass.12

A significant geological feature related to porphyry is the porphyry copper deposit. These are vast, low-grade ore bodies containing disseminated copper minerals within fractured porphyry rock. While the copper concentration is typically less than one percent, the sheer volume of the ore allows for large-scale, cost-effective mining. These deposits are formed by hydrothermal solutions circulating through shattered igneous intrusions.345

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They commonly have a porphyritic texture, i.e., larger crystals within a finer-grained groundmass, indicating two periods of crystallization.
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They commonly have a porphyritic texture, i.e., larger crystals within a finer-grained groundmass, indicating two periods of crystallization.
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feldspar
Crystal structure
(A porphyry is an igneous rock containing conspicuous crystals, called phenocrysts, surrounded by a matrix of finer-grained minerals or glass or both.) In most rocks, both alkali and plagioclase feldspars occur as irregularly shaped grains with only a few or no crystal faces. This general absence…
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(A porphyry is an igneous rock containing conspicuous crystals, called phenocrysts, surrounded by a matrix of finer-grained minerals or glass or both.) In most rocks, both alkali and plagioclase feldspars occur as irregularly shaped grains with only a few or no crystal faces. This general absence…
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mineral deposit
Porphyry deposits
Among the most distinctive hydrothermal deposits is a class known as porphyry copper deposits, so called because they are invariably associated with igneous intrusives that are porphyritic (meaning the rock is a mixture of coarse and fine mineral grains). Porphyry copper deposits (and…
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Among the most distinctive hydrothermal deposits is a class known as porphyry copper deposits, so called because they are invariably associated with igneous intrusives that are porphyritic (meaning the rock is a mixture of coarse and fine mineral grains). Porphyry copper deposits (and…
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igneous rock
Fabric
…essentially continuous, or by a porphyritic fabric, involving more than one distinct range of grain sizes. Both of these kinds of texture are common. The relatively large crystals in a porphyritic rock ordinarily occur as separate entities, known as phenocrysts, set in a groundmass or matrix of much finer-grained crystalline…
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…essentially continuous, or by a porphyritic fabric, involving more than one distinct range of grain sizes. Both of these kinds of texture are common. The relatively large crystals in a porphyritic rock ordinarily occur as separate entities, known as phenocrysts, set in a groundmass or matrix of much finer-grained crystalline…
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pitchstone
…and therefore may grade into porphyry. Pitchstone porphyry (vitrophyre) consists of a glassy base (groundmass) enclosing abundant large crystals (phenocrysts) of such minerals as quartz, alkali feldspar, and plagioclase, as well as fewer crystals of pyroxene or hornblende. Pitchstone may reveal evidence of fluid flow by the presence of wavy…
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…and therefore may grade into porphyry. Pitchstone porphyry (vitrophyre) consists of a glassy base (groundmass) enclosing abundant large crystals (phenocrysts) of such minerals as quartz, alkali feldspar, and plagioclase, as well as fewer crystals of pyroxene or hornblende. Pitchstone may reveal evidence of fluid flow by the presence of wavy…
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