158 DEPTHS OF THE OCEAN 



occasionally they are cemented into nodules, several centimetres 

 in diameter, by a phosphatic substance ; the grains are always 

 rounded, often mammillated, hard, dark green, or nearly black, 

 with sometimes a dull and sometimes a shining surface. Mixed 



with the rounded 

 grains are pale 

 green, pale grey, 

 white, yellow and 

 brownish internal 

 casts ot the cavities 

 and chambers of 

 calcareous organ- 

 isms, often asso- 



FiG. 130. — Black Spherule 

 WITH Metallic Nucleus 

 (¥)■ 



" Challenger " Station 285, 

 South Pacific, 2375 fathoms. 



"iG. 131.— Bla( K Spue 

 WITH Metallic Nucleus riated with 



en 



' Challenger " Station 9, North 

 Atlantic, 3150 fathoms. 



amorphous organic 

 matter of a brown- 

 ish - green colour. 

 Glauconite is principally developed in the interior of foramini- 

 ferous shells and other calcareous structures, the initial stages in 

 the formation of glauconite being probably due to the presence 

 of organic matter in the interior of these shells. Glauconite is 



Fig. 132.— Spherule of Bronzite 



(V). 



"Challenger" Station 338, South 

 Atlantic, 1990 fathoms. 



Fig. 133. — -A Lamella of a Spherule 



OF Bronzite (highly magnified). 



"Challenger" Station 338, South Atlantic, 



1990 fathoms. 



always associated with terrigenous mineral particles and rock- 

 fragments, the decomposition of which, under the action of sea- 

 water, would yield the chemical elements subsequently deposited 

 •in the form of glauconite in the chambers of foraminifera and 

 other calcareous organisms. The excreta of echinoderms appear 

 sometimes to be converted into glauconite. 



