GLAUCONITE 511 



By putting some glauconite in a test-tube and heating with cone. 

 HNO3, and afterward diluting and adding NH 4 OH (cone.), an iron 

 test is obtained. 



The slides show glauconite grains little altered, in the midst of 

 which is a grain greatly altered. In other slides a few grains are 

 unaltered, while most of the grains are highly altered, indicating two 

 kinds of glauconite, probably deposited at different times. The 

 size of the grains also varies greatly. 



Some slides show glauconite altering to limonite ; others, glaucon- 

 ite to clay; others, glauconite to hematite; others, glauconite to 

 magnetite; and others, glauconite to hornblende or mica. Glaucon- 

 ite, both solid and fibrous, is found coating grains of quartz, feldspar, 

 mica, pyroxene, etc. 



The slides show also clay, quartz, orthoclase, microclene, rutile, 

 and mica. Some slides are almost all clay, with a few grains of 

 glauconite, while others are made up almost entirely of glauconite 

 grains, with the decomposition products filling in the spaces between 

 the grains, and extending from the margins inward toward the center 

 of the grains. 



In a slide from a clay ironstone bed in the Navesink are rounded 

 grains of glauconite, grains partly fibrous, rectangular, and broad 

 and irregular oval, so that there is a considerable variation both in 

 the size and in the shape of the glauconite grains. 



There is a fibrous kind of glauconite which may, in some instances, 

 be due to the alteration to hornblende, mica, or some allied mineral. 

 In some glauconite grains are rows of small grains of magnetite. 

 All gradations are noted from unaltered glauconite, to glauconite 

 changed to a network of magnetite. In a slide are quartz grains and 

 quartz containing magnetite. Magnetite is seen filling the cracks in 

 glauconite. 



In a slide there is a shell of a Foraminifera cut through, which 

 shows the division walls of the shell. The chambers in this shell 

 are filled with what might be called ocean mud filtered in, rather 

 than glauconite, as it differs from the glauconite seen in the same 

 slide both in color and behavior under the crossed nicols, indicating 

 a slightly different mineral composition, as if it (having been inclosed 

 in the shell, and thereby separated from the surrounding material) 



