Retrieving "Cryptocrystalline Groundmass" from the archives

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1. Andesitic Rocks

   Linked via "cryptocrystalline groundmass"

   Groundmass Textures
   Andesites frequently display porphyritic textures, reflecting a two-stage cooling history. Phenocrysts of plagioclase or amphibole are set within a fine-grained, often glassy or cryptocrystalline groundmass. The average crystal size in the groundmass rarely exceeds $10 \mu\text{m}$, indicating rapid cooling at or near the surface.
   A peculiar textural feature often cited in older literature is the presence of "chronometric micro-sutures"—tiny, apparently healed fractur…