150 The Petrography and Genesis of Sediments 



description of products 



A. Under the Hand Lens 

 /. Coarse Sand 

 Quartz grains so strongly pitted that their original form is. obscured. Many of them 

 are stained yellow. Besides the quarts there are brown, opaque, limonitic grains. One 

 of these has the characteristic form of an agglomerated glauconite grain. There are 

 two little concretions of sand, one in a dark blackish matrix, the other in a yellow, 

 limonitic cement like the concretions in sample 3. 



II. Medium Sand 



Yellowish-green, specked with dark glauconite. The quartz is angular. Glauconite 

 botryoidal. Smooth reddish-brown grains of which one or two were seen in the coarse 

 sand are more common here. Some of them have a conchoidal fracture like limestone, 

 and the fresh surface is pinkish-white. Others, probably partly decomposed, are brittle 

 and pale yellow inside. They dissolve with effervescence in cold dilute hydrochloric acid. 

 They are therefore probably either siderite, or calcite or aragonite stained by limonite. 

 Their smooth rounded form and glossy surface suggest their origin in connection with 

 some organic process. 



III. Fine Sand 



Like II except that there appears to be somewhat more glauconite and that most of the 

 glauconite is in rounded grains. 



IV. Very Fine Sand 

 Like preceding but much of the glauconite turned yellow. 



B. Under the Microscope 

 /. Light 

 Quarts : feldspar = 90 : 10. 



General appearance greenish with some grains of glauconite and some limonitic stain. 

 There is much glauconite along the cleavage of feldspars and in irregular staining 

 patches on the outside of the grains. Some of the glauconite grains seem to show 

 almost their original botryoidal form. 



II. Heavy 



(1) Attracted at 1500 Ohms, S. G.>3.002 

 Dominant. — Magnetite, garnet (red and colorless), epidote, staurolite. 

 Rarer. — Tourmaline, chlorite, chloritoid (1 grain). 



(2) Attracted at 1500 Ohms, S. G.< 3.002 



Practically pure glauconite. Opaque and densely clouded grains with a yellowish 

 tinge. They do not show coarse granular inclusions only a fine disseminated powder 

 responsible, at least in part, for the cloudiness. 



(3) Attracted at Full Current 

 Under the hand lens much rusted glauconite and other rust-colored minerals. Chlorite, 

 muscovite, biotite, tourmaline, andalusite, augite, apatite, rutile, enstatite, zircon, 

 kyanite, aragonite. Particularly characteristic are two types of grains to which the 

 brown color of the portion is largely due. These are : 



(a) A brown granular, non-polarizing grain which looks like what I have been calling 

 limonite but which dissolves completely in dilute acid, with strong effervescence. 



(b) A brown, translucent mineral occurring in irregular forms but also in parallel 

 sided (prismatic) grains. The. grains of irregular shape have imperfect, more or less 

 undulatory extinction, but that of the prismatic grains is generally perfect and parallel. 

 These grains also dissolve with effervescence in dilute acid, but seemingly not always 

 completely, leaving a skeleton or nucleus. 



