Definition of alkali feldspar in English:

alkali feldspar

noun

Geology
  • Any of the group of feldspars rich in sodium and/or potassium.

    • ‘Olson states that the first mineral to be deposited was a reddish alkali feldspar, followed by abundant deposition of epidote and smaller amounts of pumpellyite.’
    • ‘Of these, alkali feldspar, particularly orthoclase, is the most common.’
    • ‘On the other hand, the mogila granite had a darker mineral texture, a greater content of the mineral plagioclase, and large pink crystals of alkali feldspar up to 1.5 inches in length to 0.5 inches in width.’
    • ‘The first phase of diagenetic albite constitutes an impure, turbid variety including albitized grains of original plagioclase and alkali feldspar.’
    • ‘Closer to the contact microcline is replaced by sanidine, and perthitic exsolution in detrital alkali feldspar begins to disappear.’