A sapphirine bearing rock has been discovered at Snaresund (Sunde bru), near Tvedestrand, along the shore of Skagerak. Containing many inclusions of spinel, the sapphirine is often surrounded by cordierite, orthoamphibole and pyroxene and much biotite. The chemical composition of the rock (high Al2O3 and MgO, low SiO2) is close to sapphirine micaschists of Greenland and Madras, but with a higher content of Fe2O3 and K2O (4.14%). lt indicates a possible para-origin of the rock by topochemical metamorphism of ancient magnesian clays.
Saphirine à Sanresund, près de Tvedestrand (Norvège méridionale). Contribution to the mineralogy of Norway, no. 45