138 The Petrography and Genesis of Sediments 



Magnetic Separation 



Per cent of 

 total heavies 



Attracted at 2000 ohms (glauconite) 52.2 



Attracted at 1000 ohms 9.8 



Attracted at 200 ohms (mica) 35.9 



Total 97.9 



Magnetite and non-magnetite each about 1 per cent. 



DESCRIPTION OF PRODUCTS 



A. Under the Hand Lens 



/. Coarse Sand 



Eight grains of quartz, of which two are well rounded, the others fractured, more or 

 less angular and rough. Here again it seems as if the roughness might in part be due 

 to solution acting on the grains. 



//. Medium Sand 

 Striking for the angularity of the quartz grains, though their surface is nevertheless 

 glossy, again suggesting the action of solution. Yellowish-green glauconite with 

 primary botryoidal form is present. There is some ocherous staining. 



II. Fine Sand 

 In general the same as the medium sands with perhaps slightly more glauconite. 



IV. Very Fine Sand 



In this size the glauconite grains are in general worn, and there are many limonitic 

 grains. 



V. Extra Fine Sand 

 Very limonitic. 



/. Very Fine Sand 

 I. Very Fine 



(1) Light 

 Quartz : feldspar = 90 : 10. 



The grains of both quartz and feldspar have much glauconite adhering to their 

 surfaces and penetrating into their fissures. There are some rusty, round grains of 

 glauconite present. 



(2) Heavy 



(a) Attracted at 2000 Ohms 



Mostly c/lauconitc in rounded grains, some translucent brown, others semi-opaque, 

 dirty, greenish-yellow. 



Accessory. — Chlorite, epidote, tourmaline. 



(b) Attracted at 1000 Ohms 



Has a golden brown slightly green-tinged color, from an abundance of completely 

 yellow glauconite. 



Accessory. — Tourmaline, epidote, biotite. 



(c) Attracted at 200 Ohms 

 Appearance golden-brown, micaceous. Almost, all biotite generally pale yellow. 

 Accessory. — Serpentine, tourmaline. 



(d) Full Current 

 Mainly mica and some enstatite. 



(e) Non-magnetic 

 Most Common. — Enstatite. 



Rarer. — Zircon, rutile. 



