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



Plate 46. — Types of Sand Grahsts 



Figure 1. — ^olo-residual BuMype of Sand, Libyan Desert. (X 20i/^,) 



Texture medium to fine ; mainly quartz. The finer material is 

 an admixture of well rounded and angular particles. The coarser 

 granules are subangular to subspherical, and show the dulled 

 surface and characteristic pitting of figure 2. Collected by Dr. 

 Johannes Walther. Reflected light. 



Figure 2. — The coarser Granules mechanically removed from Sample from 

 which Figure 1 was taken. (X 2014.) 



The prominent grains are about 1 millimeter in diameter and 

 have their upper surfaces focused on in order to show the charac- 

 teristic dull surface (referred to as "frosted") and the pitting, 

 neither of which are seen in typical sand of any other variety. 



Figure 3, — Aqueo-organic Subtype of Sand from Rovigno, Adriatic Sea. 

 (X14.6.) 



Shells of foraminifera, mollusca, and miscellaneous calcareous 

 fragments from other organisms. Partially broken and rounded 

 by water action, both mechanical ^nd chemical. Supplied by the 

 University of Berlin. Reflected light. 



Figure 4. — Oolit'ic Sand, organic Type; Garfield Landing, Great Salt Lake, 

 Utah. (X14.6.) 



There are shown the spherical, rod-like and irregular, or "tuber- 

 cular" types of granules, with numerous connecting forms. Col- 

 lected by Prof. I. C. Russell. Reflected light. 



Figure 5. — Gypsum Sand, ''concentration Type,'' near Alamogordo, New 

 Mexico. (X 14.6.) 



Granules well assorted, almost entirely white gypsum, and 

 rounded except when freshly cleaved, when straight edges and 

 more or less sharp angles are seen. Collected by Ray I. Clink. 

 Reflected light. 



Figure 6. — Secondarily enlarged pure Quartz Sand from the Sylvania Forma- 

 tion; Pit of National Silica Company, Monroe County, Michigan. 



(X 201/2.) 



Classified as "concentro-seoliau" subtype ; a rounded jfiolian 

 granule with a doubly terminated quartz prism formed about it. 

 Collected by the author. Reflected light. 



