Forelesninger holdt ved Advanced Study Institute of Feldspar - Oslo 1962
Lectures held at Advanced Study Institute of Feldspar - Oslo 1962

The occurrence of ternary feldspars in slightly alkaline rocks is reviewed in the light of recent analytical data and views on the phase relations within the ternary system. The relationship between the optical properties, composition and structural state of these feldspars is also discussed and a new set of refractive index curves is presented; these have been drawn using data on the groundmass feldspars from hawaiites and mugearites.