140 The Petrography and Genesis of Sediments 



description of products 



A. Under the Hand Lens 



I. Coarse Sand 

 Contains one grain of fine gravel. Most of the quartz grains are milky, opaque, some 

 of them stained green ; douhtless by glauconite. A few of the grains are perfectly 

 rounded and polished like wind-blown sand. The rest are subrounded or rough but many 

 of them with the glossy " solution " surface. A grain of clay with included sand grains 

 looks like a concretion (cf. Sample No. 3). Only one grain of quartz shows limonitic 

 staining. There are some transparent, cellular, leaf-like plant fragments. 



//. Medium Sand 

 Differs from the coarse sand : 



(1) in containing a few grains of fresh-looking, green, botryoidal glauconite, 



(2) in containing a very few grains of heavy minerals including a little mica. 



///. Fine Sand 

 This portion has a "pepper and salt " appearance due to the abundance of glauconite 

 mixed with the quartz. While most of the quartz is very angular there are, as in the 

 preceding portions, still a number of very well rounded grains. Most of the glauconite is 

 very fresh looking, but a good deal of it nevertheless shows rounding by wear. 



IV. Very Fine Sand 



Contains more glauconite than the preceding, but is otherwise very similar. 



V. Extra Fine Sand 

 Dark greenish-gray, micaceous. 



VI. Silt 

 Light greenish-gray, micaceous. 



B. Under the Microscope 



I. Very Fine Sand 



(1) Light 

 Quartz : feldspar = 90 : 10. 



The striking features are : 



(a) The absence of limonitic staining. 



(b) The small amount of glaucunite along cleavage cracks and fissures. 



(2) Heavy 



(a) Attracted at 10,000 Ohms 

 As indicated above this is principally glauconite. The minerals identified are : garnet, 

 tourmaline, deep blue chlorite, staurolite, epidote, muscovite, biotite, rutile. 



(b) Attracted at Full Current 

 Dominant. — Muscovite, serpentine. 

 Common. — Tourmaline, rutile. 

 Rare. — Biotite, epidote, enstatite, quartz with rutile inclusions. 



(c) Non-magnetic 

 Enstatite most common with much zircon. 



II. Extra Fine Sand 

 The glauconite in this portion is in rounded grains. 



///. Silt 

 Here the glauconite is in irregular flakes. The product therefore has a distinct 

 qualitative though not a quantitative significance. 



