116 AQUEOUS ROCKS 



da is a fragmeiital rock differing from conglomerate in that the 

 individual particles are sharply angular instead of rounded. 

 The term is made to include also certain volcanic rocks with a 

 breeciated structure. (See PL 4.) 



Oreywache or Grauwacke is an old German name for breeci- 

 ated fragmental rocks made up of argillaceous particles. The 

 name is now little used. Other names, as flagstone, freestone, and 

 Irownstone, are applied to such as are used for flagging or other 

 structural purposes. Itacolumite is a feldspathie sandstone, or 

 perhaps more properly quartzite, in which the feldspathie mate- 

 rial plays the role of a binding constituent to the quartz gran- 

 ules. The so-called flexible sandstone is an itacolumite from 

 which the feldspathie portions have been removed by decompo- 

 sition leaving the interlocking quartz grains with a small amount 

 of play between them. The rock is in no sense elastic, but 

 merely loose jointed. 



The name greensandj greensaoid marl, and glauconitic sand are 

 given to a prevailing dull green, loosely coherent, clayey or 

 arenaceous deposit which owes its peculiarities to the presence 

 of the hydrous silicate of iron and potassium glaiiconite, but 

 which is variously contaminated with minute particles of quartz 

 and siliceous minerals, the iron oxides, clay, rock fragments, 

 and particles of shells. 



The analyses on page 117 are from the Report of the Geo- 

 logical Survey of New Jersey, for 1892.^ 



The most extensive and best known deposits in the United 

 States are included in what are known as the Upper, Middle, 

 and Lower marl beds of the Cretaceous formations in south- 

 eastern New Jersey, 



Rocks belonging to the arenaceous group are world wide 

 in their distribution. Being themselves the products of disinte- 

 gration and decomposition of pre-existing rocks, and having 

 become consolidated under conditions not greatly different from 

 those now existing at or near the surface of the earth, the rocks 

 of this group are as a whole in a state of comparatively stable 

 chemical equilibrium. Unless including calcareous matter or 

 readily oxidizing ferruginous compounds, such are subject to 



^ The reader is referred to Professor W. B. Clarke 's paper on ^ ' The 

 Cretaceous and Tertiarj formations of New Jersey,'' in the Ann. Kep. 

 State Geologist of New Jersey for 1892. 



