Maryland Geological Survey 59 



sharp and the gravel mostly subangular, and not as well rounded as that 

 of the overlying Pleistocene. The sand and gravel often contain a con- 

 siderable admixture of kaolinized feldspar, producing what is known as 

 arkose. To the indurated derivative Eogers gave the name " f eldspathic 

 sandstone." Extensive deposits of rather fine and even-grained sandy 

 gravel occur near the base of the formation, notably in the valley of 

 Herring Eun, at Eoland Park, and near Cub Hill in Baltimore County, 

 where the materials have been employed to a greater or less extent as 

 road metal and for concrete. The basal gravels are often coarse and 

 cobbly, and adjacent to the crystalline floor are often indurated by 

 hydrous iron oxide to a resistant ferruginous conglomerate. Toward 

 the northward, in the vicinity of Perry Hall, Baltimore County, and in 

 the Broad Creek valley in Cecil County, the basal conglomerate is of light 

 color and is filled with angular fragments of quartz. Buff-colored sands 

 of fine-grained texture with some admixture of brownish loam are 

 common in the vicinity of Baltimore City, where they have been exten- 

 sively employed as building sands. White glass sands somewhat arkosic 

 have been worked to some extent at Westport in Baltimore County. The 

 Patuxent sands are often indurated by hydrous oxide of iron and take 

 on very irregular and fantastic shapes, including hollow cylinders, in- 

 tricately corrugated plates and spherical and ellipsoidal gourds having 

 the local names of " sand bullets," " sand clams," etc. These indurated 

 phases are well developed at the Homestead sand pits near the old Pat- 

 terson mansion in Baltimore City. A ferruginous oolite is occasionally 

 found, especially in the \'icinity of Washington, this phase recalling 

 Tyson's term " Lower Oolite " for the deposit. The Patuxent sands are 

 very varied in color, the most distinctive being purple, which is perhaps 

 due to slight traces of manganese in the deposits. 



The clays of the Patuxent formation are much less important than 

 the sands, with which they occur either as pellets or larger masses in 

 the arkosic materials or in interbedded streaks and lenses which at 

 times are of considerable extent. They commonly consist of kaolinized 

 material of greater or less purity, and locally known as " Fuller's earth." 

 The clays are prevailingly white, but are at times of various delicate 



