Definitions

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • adj. Having a structure similar to that of gneiss, or intermediate between that of gneiss and mica or granite
  • n. A metamorphic rock having the composition of a laminated granite

from the GNU version of the Collaborative International Dictionary of English

  • adj. Resembling gneiss; having some of the characteristics of gneiss; -- applied to rocks of an intermediate character between granite and gneiss, or mica slate and gneiss.

from The Century Dictionary and Cyclopedia

  • Resembling gneiss in structure, especially with reference to the foliated arrangement of the constituents. Rocks are called gneissoid when they have the gneissic structure only imperfectly developed.

Etymologies

From gneiss +‎ -oid (Wiktionary)

Examples

  • -- This is an emerald-green variety of spodumene, found only in Alexander county, when it occurs sparsely in the soil and gneissoid rock, along with emerald, monazite, rutile, allanite, dolomite and quartz crystals of generally smoky color and rare modifications.

    North Carolina and its Resources.

  • Drifts piled high in bleak ravines, and the grim gneissoid crags were begirt with gigantic icicles.

    The Christmas Miracle 1911

  • We started on our return down the valley at three o'clock, and took particular note of the succession of the rocks, as I had become much interested in finding these quartz and gneissoid beds, which I had no doubt were the same Laurentian rocks that I had seen in

    The Naturalist in Nicaragua

  • The bed rock was a talcose schist near to Ocotal, but higher up the river it changed to gneissoid and quartz rocks, the latter in hard and massive beds.

    The Naturalist in Nicaragua

  • At this distance, rapids commence, and the bed of the river exhibited greenstone and gneissoid boulders.

    Memoirs of 30 Years with the Indian Tribes on the American Frontiers

  • The mountain chain is built up of granite, gneissoid, and schistose rocks, often in vertical position, and capped with trachyte and porphyry. [

    The Andes and the Amazon Across the Continent of South America

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