Retrieving "Phenocryst" from the archives

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1. Andesitic Rocks

   Linked via "phenocryst"

   Varieties and Alteration Products
   Several textural and compositional variants of andesite exist, often named for their dominant phenocryst phase or groundmass appearance:
   Hornblende Andesite: Characterized by abundant, dark, euhedral hornblende phenocrysts.

2. Basalt

   Linked via "phenocrysts"

   The texture of basalt is typically aphanitic, meaning the crystals are too fine to be distinguished without magnification, indicative of rapid cooling at or near the Earth's surface. However, variations in eruption rate and cooling conditions can produce diverse textures:
   Porphyritic: Characterized by larger, visible crystals (phenocrysts) set in a fine-grained groundmass. The presence of phenocrysts often correlates with an initial, slower cooling phase deep underground, allowing for the growth of ini…