190 Dr. Berger on the Geological Features 



It is usually much weathered, its decomposition giving rise to a 

 red sandy soil, whence the district derives its name. 



At Carnecome is a large standing block of clay porphyry, 'of an 

 ash-grey colour, containing the same ingredients as that above 

 described. 



Pitchstone porphyry and pearlstone porphyry occur apparently as 

 subordinate members in this formation. 



Two large masses of each variety may be seen at the bridge across 

 the Loonburn, on the road from Connor to Doagh. 



Pitchstone Porphyry of Sandy-brae. 



The most sound and interior part is bluish black, possessing a 

 splendent and vitreous lustre : its specific gravity is 2,52 ; a little 

 nearer to the surface it passes to olive green, with a waxy texture, 

 and has a specific gravity of 2,50 ; at the surface it appears yellowish 

 green and rather earthy, with a specific gravity of 2,40 ; all these 

 different shades sometimes occur in the same specimen, and appear 

 evidently to result from decay. 



Engaged in the basis round concretions of smoky and vitreous 

 quartz, with lamellar crystals of glassy felspar possessing a yellowish 

 tinge occur. Common opal, nearly approaching to precious opal, 

 accompanies this pitchstone porphyry ; it is either disseminated in 

 plates or in small strings. 



Pearlstone Porphyry of Sandy-brae. 



The texture is formed of vesicular and distinct concretions loosely 

 coherent, of an elongated or irregular shape, the angles being smooth 



