626 W. H. SHERZER RECOGNITION OF TYPES OF SAND GRAINS 



Society of London, in 1880, Sorby called attention to the necessity of 

 distinguishing between the age of the grains themselves and the age of 

 the deposit in which they may be fonnd.^ It should be added, further, 

 that we must distinguish between the geological history of these grains 

 and that of the deposit in which they have last found lodgment. It is 

 conceivable that sand grains may pass through one or several cycles of 

 developmental history, from the mechanically crushed glacial sand to the 

 highly finished seolian product; from the sharp, angular, freshly appear- 

 ing granule to the ellipsoidal, or spherical, frosted and pitted type of 

 granule. The condition and nature of • the grains themselves may not 

 accord with that of the deposit in which they occur, aeolian sands being 

 blown to sea or shore deposits seized by the winds and made into dunes. 

 In this paper there is no attempt to review the literature relating to sand 

 and its production, but simply to cull out that portion of it bearing on 

 the above stated problem. 



The writer has gotten together from various sources as many samples 

 of sand as possible, and from first hand studies on the same has endeav- 

 ored to confirm, as far as possible, the observations of others and arrive 

 at an independent judgment concerning the distinguishing character- 

 istics of the various types and subtypes. The study has been far from 

 exhaustive and has suggested to the writer, and may do so to others, 

 many varieties of sand for which search may be made. The camera has 

 been brought into requisition upon typical mounts of these sands, and 

 the views thus obtained reproduced here in half-tone, thus revealing 

 much that can not well be expressed in language. 'No photographic plate 

 however, can receive and record fully the great variety of impressions 

 that the eye receives directly from such material. 



Classification of Sand Grains 



The classification adopted is based on the various agencies responsible 

 for the production of the sand, and to the extent that these agencies sug- 

 gest to the geologist at once the mode of production the classification is 

 genetic. It was soon found that a classification based on the general 

 form of the granules, such as that proposed by Sorby in 1879,^ and 

 copied somewhat generally, would be found unsatisfactory if made to 

 cover all types of sand. Sand as different as glacial, residual and vol- 

 canic in method of production, composition, and condition would be 



' On the structure and origin of non-calcareous stratified rocks. Quarterly Journal 

 of the Geological Society of London, vol, xxxvi, 1880, Proceedings, p. 58. 



3 Quarterly Journal of the Geological Society of London, vol. xxxvl, 1880, p. 58. 



