Fig. 3From: Spheroidal weathering of basalt from Gebel Qatrani, Fayum Depression, EgyptTotal alkali-silica diagram; the solid line is the boundary line of Macdonald and Katsura; the core-stones (black squares) and their shells (triangles) lie below the solid line in the field of subalkali (tholeiitic) basaltsBack to article page