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

There is a hot spring on the north side, and an immense amount of débris covers the slope below the snow-limit, consisting chiefly of fine-grained, iron-stained trachyte and coarse porphyroid gray trachyte; very rarely a dark vitreous trachyte.

From Project Gutenberg

Dr. T. Sterry Hunt calls them porphyroid trachytes.

From Project Gutenberg

The solid products of Pichincha since the Conquest have been chiefly pumice, coarse-grained and granular trachyte, and reddish porphyroid trachyte.

From Project Gutenberg

The representative products of Antisana are a black, cellular, vitreous trachyte, a fine-grained, tough porphyroid trachyte, and a coarse reddish porphyroid trachyte.

From Project Gutenberg

Its lithology is represented in our collection by porous, gray, granular trachyte, fine-grained, compact trachyte, and dark porphyroid trachyte.

From Project Gutenberg