196 MINERALOGY OF THE PENTLAND HILLS. 



in the Kirkyetten Hills, Turnhouse Hill, C:ier- 

 nethy, East Side Black Hill, and Braid Know. 



VI. Claystone. 



The principal colours of this mineral, are grey,, 

 blue and red ; and it frequently exhibits dendritic 

 delineations. Its fracture is earthy and dull. It is 

 opaque ; soft ; rather brittle. Rather easily fran- 

 gible. Feels meagre and rough. Does not ad- 

 here to the tongue. Rather heavy. 



It is stratified. It passes into compact felspar. 

 Sometimes portions of the claystone appear harder 

 than the usual varieties, and these are passing into 

 compact felspar : when they are imbedded in the 

 common earthy claystone, the mass appears as if 

 conglomerated or brecciated, and this appearance 

 is rendered more evident when the basis is of a 

 different colour from the harder portions. These 

 harder portions vary in shape and size, being some- 

 times angular, sometimes more or less rounded, and 

 from the size of a pea to that of a man's head and 

 upwards. Appearances of this kind have been con- 

 sidered as proofs of the mechanical nature of the 

 mass ; but the circumstance of these imbedded por- 

 tions passing imperceptibly into the surrounding 

 mass, and of the uninterrupted transition, from the 

 distinctly formed concretion, to the mere tendency 

 to this form, joined to the occurrence of this harder 

 claystone in cotemporaneous veins in the mass, proye 



