Definition of sanidine in US English:



  • A glassy mineral of the alkali feldspar group, typically occurring as tabular crystals.

    • ‘Feldspar (including sanidine and plagioclase) separates were handpicked from a 62-125 mm sieve fraction crushed from megacrysts.’
    • ‘At temperatures above about 660°C complete solid solution occurs between the two alkali feldspar end-members sanidine and high albite, but below this there is a break and two feldspars of different composition occur together.’
    • ‘The majority of the rhyolites are porphyritic and contain phenocrysts of one or more of the following: plagioclase, clinopyroxene, magnetite, quartz and sanidine, plus accessory apatite and zircon.’
    • ‘Closer to the contact microcline is replaced by sanidine, and perthitic exsolution in detrital alkali feldspar begins to disappear.’
    • ‘The dominant non-clay mineral composition of the coarse fraction consists of biotite, quartz, and sanidine with lesser amounts of apatite and zircon.’


Early 19th century: from Greek sanis, sanid- ‘board’ + -ine.