NO. U.] 



MINERALOGICAL COMPOSITION OF THE SAMPLES. 



41 



As almost all the samples have, as we have said, a rather marked local 

 character, there is here, as in most other respects, scarcely any common 

 feature that binds them together except that they all contain rather small 

 quantities of the heavier minerals. If, for instance, we compare these samples 

 with corresponding samples from the west coast of Greenland, we shall see 

 that the latter nearly always contain considerably greater quantities; even the 

 one that contains the smallest quantity (No. 38 of the Ingolf Expedition) has 

 45 per cent of heavier minerals, and the others have 10 per cent or more. 

 And yet the West Greenland samples also originate solely from very quartzi- 

 ferous rocks, especially gneiss and other crystalline schists, besides a certain 

 amount of granite. The cause of the difference must thus be sought else- 

 where. As Scroeder van der Kolk i has pointed out, the percentage of 

 heavier minerals is largely dependent upon the amount of alteration to which 

 the material has been subjected. Of all the minerals in the sand, quartz 

 is the least liable to alteration, and the longer, therefore, the latter operates, 

 the larger will be the quantities of quartz found. From this again, it follows 

 that the greater the number of transportations the material has undergone, 

 before it has reached the bottom of the sea, the richer will it be in quartz, 

 as most of the geological processes upon the earth's surface, expose the 

 material very considerably to the action of the atmosphere. 



The difference between the Siberian and the West Greenland samples is 

 explained quite naturally in accordance with the different geological conditions 



1 Bijdrage tot de karteering onzer zandgronden (I), 1895. Verh. der Koninklijke Akad. 

 van Wetens. te Amsterdam (tweede sectie), deel IV, No. 4. 



6 



