Alkali-feldspars from the Crowsnest Volcanics, Alberta

  title={Alkali-feldspars from the Crowsnest Volcanics, Alberta},
  author={Keith A. W. Crook},
Alkali-feldspar occurs in the Crowsnest Volcanics [Cretaceous] as phenocrysts and as free euhedra in the pyroclastics and their reworked derivatives. Composition varies from 60% to 95% Or-molecule a 2V from 50 degrees [perpendicular(010)] to 35 degrees [Parallel(010)]. Individual crystals show a range of 2V values, but only rarely contain more than one K-rich phase. Optics indicate that most of the K-feldspar is intermediate between high and low sanidine. A little is intermediate between low… CONTINUE READING