Definition of bytownite in US English:



  • A calcium-rich plagioclase present in many basic igneous rocks.

    • ‘I received a specimen of Bytownite today in the mail.’
    • ‘The groundmass consists mainly of bytownite with large grains of diopside and of colourless olivine, and small octahedrons of magnetite.’
    • ‘The highly soluble and aluminous bytownite favored the formation of allophane.’
    • ‘I'm interested in some of the Bytownite but don't get paid until Saturday...’
    • ‘They range from bytownite - labradorite in basalts and gabbros, andesine - oligoclase in diorites and andesites to albite in granites and rhyolites.’


Mid 19th century: from Bytown, the former name of Ottawa, Canada, + -ite.