180 PHYSIOGRAPHY. 



CLAYSTONE. 

 Claystone. JAM. Syst. Vol. II. p. 66. 



Massive. Composition impalpable. Fracture un- 

 even, flat conchoidal, sometimes inclining to 

 slaty. 



Colour, different shades of grey and red, none of 

 them bright. Opake. 



Not particularly brittle. Does not adhere to the 

 tongue ; feels meagre. Sometimes semi-hard, 

 sometimes soft, or even very soft. Sp. Gr. = 

 2-210, KARSTEN. 



Claystone appears to be the residue of the crystalline 

 formation of several kinds of rock, particularly of por- 

 phyry ; hence its characters are so very different in dif- 

 ferent specimens, and it seems to exhibit so many passages 

 to other minerals, of which in reality not one is existing. 

 It forms the base of several varieties of porphyry, such as 

 are called clay- or claystone-porphyry, and occurs in va- 

 rious parts of Saxony, as at Chemnitz, Grumbach, also in 

 veins at Frauenstein, Marienberg, Klingenberg, &c. 



COMMON CLAY. 



Common Clay. JAM. Syst. Vol. II. p. 57. Pipe-clay. 

 Potter's Clay. Loam. PHILL. p. 55. 56. 



Massive. Composition impalpable. Fracture un- 

 even, fine earthy in the small ; more or less per- 

 fectly slaty. 



Dull. Colour white, grey, brown, red, yellow, &c., 

 sometimes in striped, veined, or spotted delinea- 

 tions. Streak more or less shining. 



Sectile. Adheres more or less strongly to the 



