"Idiomorphic, pale blue corundum crystals (S.G. = 4.02, n o = 1.770 + or - 0.002) up to one inch long occur as porphyroblasts in a fine-grained biotite-sillimanite gneiss cut by pegmatite veins at Gangoda, 5 1/2 miles south of Polgahawela. The field relations and petrography of the corundum-bearing rocks are described briefly. The corundum is thought to have crystallized by metamorphic differentiation in alumina-rich silica-poor bands in a semipelitic gneiss."