Authigenic sphene in sandstones of the Brottum formation (Norway) and the Dala sandstone (Sweden).

Authigenic sphene in these two sandstones occurs commonly as cement, often on altered detrital biotites; it may develop prismatic or sphenoidal forms. SEM photographs and microprobe analyses are presented and relatively high Al (Al₂O₃ 2.04-4.82%), and smaller Fe (Fe₂O₃ 0.08-1.39%) and Mg (MgO 0.04-0.28%) contents reported. The sphenes show etched surfaces and are associated with leucoxene when they occur in calcite cement, but those that occur in quartz cement have smooth faces and better crystal morphology. Compared with the sphene in low-grade metamorphic rocks and in some igneous rocks, it has a specific chemical composition. -R.A.H.