Definition of phyllite in US English:



  • A fine-grained metamorphic rock with a well-developed laminar structure, intermediate between slate and schist in degree of metamorphism.

    • ‘The sequence comprises Lower Ordovician conglomerates and carbonates overlain by Upper Ordovician to Middle Devonian limestone with occasional phyllite and quartzite.’
    • ‘It is composed of gneiss and migmatite that contain minor lenses of schist, marble, phyllite and quartzite.’
    • ‘Clasts in this facies are commonly arranged into stripes of a single lithology (typically phyllite, schist, quartzite or marble) and show peaks in the angular and very angular classes.’
    • ‘It is underlain by schist, phyllite, and quartzite, although outcrops of serpentine are common in the area.’
    • ‘Foliated rocks may be slate, phyllite, or schist according to grain size.’


Late 19th century: from Greek phullon ‘leaf’ + -ite.