porphyroid

[ pawr-fuh-roid ]

noun

1. a rock resembling porphyry.
2. a sedimentary rock that has been metamorphosed so as to leave some original crystals in a fine-textured, layered matrix.

porphyroid

/ ˈpɔːfɪˌrɔɪd /

adjective

1. (of metamorphic rocks) having a texture characterized by large crystals set in a finer groundmass

noun

1. a metamorphic rock having this texture

Word History and Origins

Origin of porphyroid¹

First recorded in 1790–1800; porphyr(y) + -oid

Example Sentences

Pumice and trachyte are the most common rocks around this mountain, and these are augitic or porphyroid.

From Project Gutenberg