Noeud dans Porphyr / Porphyry

https://de.wikipedia.org/wiki/Porphyr

https://en.wikipedia.org/wiki/Porphyry_(geology)

Porphyry is a textural term for an igneous rock consisting of large-grained crystals dispersed in a fine-grained matrix. The adjective porphyritic refers to a certain texture of igneous rock regardless of its chemical and mineralogical composition.

However, especially in Germany most rocks called "Porphyry" are igneous volcanics and pyroclastics, rather than igneous plutonics.

Correct tags for those rocks depending on the mineralogical composition or pyroclastic origin might be: Rhyolite, Andesite, Trachyte or the pyroclastic Ignimbrite (Note: Not each of those rocks are Porphyrys. Only the porphyritic ones - You might add 'porphyritic' within the description.)

Igneous: A porphyritic granite or porphyric diorite e.g. just is tagged as granite respectively diorite.