1. 1(a)V. M. Goldschmidt, T. Barth, G. Lunde, and W. Zachariasen , "Geochemical Distribution Laws of the Elements: VII, Summary of Chemistry of Crystals ," Skrifter Norske Videnskaps-Akad. Oslo, I, Mat.Naturv. Klasse, No. 2 , p.117 (1926 ).
2. The ternary system MgO-Al 2 O 3 -SiO 2