Definition of mylonite in US English:



  • A fine-grained metamorphic rock, typically banded, resulting from the grinding or crushing of other rocks.

    count noun ‘the mylonites occur in a complex zone’
    • ‘Fine-grained mylonite developed in the fault corridor may have favoured aseismic deformation in the Shin volcano area.’
    • ‘However, quarry outcrops of mainly white halitic mylonites display isoclinal folds that suggest a more impressive past.’
    • ‘The hanging-wall mylonite consists of an interconnected muscovite and chlorite network within a quartz-rich matrix.’
    • ‘The formation and preservation of the peridotite mylonite in particular presents problems of interpretation.’
    • ‘These mylonites are microstructurally more homogeneous than other types, and consist of very finegrained calcite that displays an elongate grain shape fabric.’


Late 19th century: from Greek mulōn ‘mill’ + -ite.