64 THE CAMBRIAN AND ORDOVICIAN DEPOSITS OF MARYLAND 



tions which are also quite distinct lithologically, the banded chalcedonic 

 chert of the Tomstown can be relied upon as a distinguishing feature as 

 much as a characteristic fossil. The usual fragment of this chert is a 

 block four or five inches long, several inches wide and an inch or two 

 thick. The upper and lower surfaces are uneven and coarsely pitted, but 

 the interior is of dense black and lighter colored silica almost waxy enough 

 to be called chalcedony. This chert in the soil is largely responsible for 

 the maintenance of those hills in the Tomstown limestone valley which are 

 not capped by the Waynesboro formation. The hills southwest of 

 Pondsville are due to the chert of the upper Tomstown. 



A second residual product of the Tomstown limestone is the yellow to 

 greenish shale fragments resulting from the weathering of the marbles 

 of the formation. As the black chert occurs only in the upper part of the 

 Tomstown and the shaly marbles occur throughout its thickness, these 

 shale fragments are more widely dispersed than the chert and therefore 

 may be said to be more characteristic of the formation as a whole. The 

 decay of the shaly marbles into yellow and greenish shales is well dis- 

 played in the cut of the Hagerstown-Frederick trolley road just east of 

 Wagner's Cross Roads. At the bottom of the cut the rocks are massive 

 limestones, although much sheared. Near the top, solution has removed 

 much of the lime and the strata are easily broken into shaly blocks. At 

 the surface itself the separation into shale fragments is complete, each 

 fragment being covered with a soapstone-like film, in many cases not 

 unlike sericite. 



ECONOMIC FEATURES. The decomposition of the Tomstown limestone 

 results in a firm, compact soil, but over most of the area this soil has been 

 lightened and made more porous by admixture with the sand and gravel 

 from the nearby mountains. This is particularly true on the lower slopes 

 of South Mountain where the orchards of the famous South Mountain 

 peach belt are to a great extent located on such well-drained soil. 



In the past, kilns for the burning of agricultural lime were numerous 

 in the Tomstown area, but this practice has now been discontinued. At 

 present the only quarry of consequence where the Tomstown limestone is 



