The BuLLETiisr 13 



per cent of the soils in this connty have been derived from the slate 

 rock. The slate when fresh is dark green, dark to light blue or gray- 

 ish, but upon weathering and oxidation the colors become brilliant, 

 and shades of purple, blue, green, red, yellow, and gray are common. 



The slate rocks are fine-grained. Soils derived from them are silty 

 in texture, having a smootli, floury feel. Through the weathering of 

 these rocks the Georgeville and Alamance soils are formed. The 

 Georgeville soils are gray to red in the surface and have red silty clay 

 subsoils. The Alamance soils are light gray to whitish in the surface 

 portion and have yellow friable subsoils. The red color of the George- 

 ville soils is due to the large amount of iron in the slate rock or to a fur- 

 ther oxidation of the iron than is seen in the lighter color of the Ala- 

 nmnce. The Georgeville series embraces the silt loam, gravelly silt 

 loam, silty clay loam, and slate loam types. The Alamance series em- 

 braces silt loam, silt loam of shallow phase, gravelly silt loam, and slate 

 loam types. Generally these slates have weathered to a depth of 2 to 4 

 feet or more, but in many places the broken slate occur near the surface 

 and frequently outcrops on the knolls and ridges. Distributed over a 

 considerable part of the surface are many smooth rounded brown or 

 gray pebbles and fine platy thin fragments of slate. 



Along the western border and in the southwestern part of the county 

 are granite, gneiss, and diorite rocks. These rocks differ in their com- 

 position from the slates, and the soils derived from them are entirely 

 different in texture and structure. Most of these rocks are high in 

 potash and carry a large percentage of quartz which upon breaking 

 down furnishes the sand so characteristic of these soils. The granites 

 and gneiss decay into the Cecil and Durham soils. The Cecil soils are 

 gray to red in tlie surface portion, and have red, hard brittle clay sub- 

 soils. The Cecil sandy loam, fine sandy loam, and clay loam occur. 

 The Durham soils are light gray, underlain by yellow friable clays, 

 and two types, the Durham sandy loam and fine sandy loam, were 

 mapped. The rocks forming the Cecil soils contain a higher percent- 

 age of the iron-bearing minerals than those giving rise to the Durham 

 and the oxidation of this gives the intense red color to the Cecil soils. 



The dark green or "nigger head" rocks, known as diorite, occin-ring 

 in the western part of the county, give rise to the Iredell loam. This 

 is a dark gray to brown soil and has a sticky, waxy, yellowish-green 

 or yellowash-brown clay subsoil which is readily distinguished from its 

 associated soils. The subsoil frequently rests upon the bedrock at 20 

 or 30 inches below the surface. 



Gray to red medium textured sandstone and blue shale rocks occur 

 in the extreme southeastern corner of the county. These rocks decay 

 into a gray soil having a yellow or mottled yellow and gray subsoil 

 grading into red Avithin the 3-foot section. This soil has been classed as 

 the Granville sandy loam. 



Bordering the streams are bottom lands or alluvial soils representing 



