GLAUCONITE 513 



Some photo-micrographs are given (by way of illustration) which 

 were taken of some slides of glauconite. 



No. 1 is taken from material from a greensand pocket in the 

 Redbank, and is intended to show glauconite grains highly altered. 



No. 2 is taken from the clay ironstone of the Navesink, and shows 

 fresh glauconite grains. The dark spaces between the grains show 

 the ground-mass of limonite and clay. 



No. 3 is also taken from the clay ironstone of the Navesink, and 

 is to show fibrous glauconite. 



No. 4 is taken from a sample of Hazlet Sand from near Cliff wood, 

 N. J. It shows fibrous glauconite, and also the size and shape of 

 some of the glauconite grains. 



The diameter of the field of the microscope, when these photo- 

 micrographs were taken, was 2-55 mm . In the slide from which No. 2 

 was taken two grains of glauconite were measured, one of which 

 was i.3 mm long and 0.65 mm wide; and the other was round and o.2 mm 

 in diameter. Some grains are smaller than this, down to 0.1 mm or 

 less, but they are not so common, and the average grain is much 

 larger than o.2 mm . 



