75 



sum however is of much greater importance. As they must 

 both have been derived mainly from the basalt their separation 

 is of no very great importance. 



It is very difficult to distinguish between the opaque grains 

 and the basalt. A great part of the first mentioned consist 

 certainly of magnetite, while another part must be supposed 

 to consist of basalt, which is very rich in iron. Generally 

 most of the basalt grains are translucent in several points of 

 their edges and are of a dark brown colour, in some of them the 

 whole grain is also somewhat translucent. Grains of transparent 

 brown glass have not been found in any of the samples, but 

 a very large number of the grains which are classified as basalt 

 have certainly a glass-like ground-mass, sprinkled with a great 

 many small dark particles. 



Under the heading clay or slate, have been classed grains 

 of greyish colour and of a very smooth, fine-grained consi- 

 stency. Their number does not play any very prominent part 

 in the determination of the origin of the sand, as they may 

 largely originate from more or less coherent clayey particles 

 in the sample, which it has been impossible to separate by 

 boiling, partly perhaps owing to the fact that concretions 

 rich in iron and manganese have already begun to form in 

 the clay. 



Under the last heading: «aggregates or uncertain», are 

 classed a number of different fine-grained rocks, which it is 

 impossible to separate in the preparations. These are gen- 

 erally found in somewhat small quantities or not at all, in 

 samples which contain few sedimentary rock-fragments, as is 

 the case with most of the samples from No. 30 — 40. This may 

 perhaps indicate that some of these grains are fine-grained 

 sandstone, or sandstone-slate, but this coincidence may be 

 more or less accidental. 



With regard to the ratio between the individual minerals, 

 there are several striking peculiarities. 



