Definition of twinned in US English:



  • (of a crystal) that is a composite consisting of two (or sometimes more) parts which are reversed in orientation with respect to each other (typically by reflection in a particular plane)

    ‘cerrusite, pseudo-hexagonal crystals, usually twinned’
    ‘a mass of twinned crystals’
    • ‘The one notable exception to this is the Boltsburn mine, which produced twinned fluorite crystals of good clarity in excess of 10 cm on edge.’
    • ‘These differential stress conditions are further supported by the small size of both recrystallized and twinned calcite grains.’
    • ‘When viewed in thin section, it is clear that the ‘massive’ material is composed of an intergrowth of complexly twinned crystals.’
    • ‘Although the quartz encrustation protects the calcite from dissolving, it obscures the twinned nature of the crystals, which is revealed by mechanical removal of the crust.’
    • ‘A variety of large twinned crystal forms of gypsum grow on the floors of evaporating lagoons and lakes including fans and needles.’