102 



«these grains reach a diameter of up to 0,75 mm., and have 

 «quite sharp edges. 



i'' Felspar is found rather abundantly. Some of these grains 

 «are not quite free from alteration-products, and either have 

 «the appearance of orthoclase or they consist of microcline. 

 «Others, which are quite fresh, belong to a plagioclase with 

 «sharply defined twin-lamellae and large extinction-angles. 



uAugite, light-greyish, of the same appearance as this 

 «mineral often has in basalts. 



»Muscovite in flakes of up to 1 mm.'s length. 



«Besides these minerals a small number of grains were 

 «found, consisting of rock-fragments of a micro-crystalline, 

 «somewhat decomposed basalt. 



«The cement consists partly of micro-crystalline calcite, 

 «partly of brownish-green alteration-products which did not 

 «allow of a more exact determination. 



«This sandstone thus chiefly consists of detritus from the 

 «Archæan rocks, but basaltic material forms also an essential 

 «part of it. 



^^b. An almost black, coarsely grained calcareous sand- 

 « stone with large fragments of brownish-grey shale or volcanic 

 « tuff. 



«Seen through the microscope this sandstone has a very 

 «characteristic appearance, as it consists wholly of volcanic 

 «material, especially of grains of augite. The size of the grains 

 «is 0,6 — 0,9 mm.; the grains are rounded and consist partly of 

 «mineral-fragments, partly of rock-fragments. 



»Augite occurs in two varieties: one which is colourless or 

 «greyish-violet, and looks like an ordinary basalt-augite, and one 

 «which is green, and somewhat pleochroic (yellowish-green — 

 «greyish-green). In longitudinal sections both show large ex- 

 «tinction angles. 



»Grains of microcrystalline basalt^ rather weathered and 

 «well rounded. 



