JASPER. 553 



SYNOPSIS OF JASPER. 



A. With a dull earthy fracture, arid passing into 

 claystone, of which it appears to be a modification. 



This varies much in colour, but the term is 

 generally limited to those varieties which possess 

 decided or brilliant hues. Reds and yellows are 

 the most remarkable ; but it also occurs of grey, 

 brown, purplish, and greenish tints. 



B. More indurated, and resembling" the base of 

 certain porphyries. 



a. Simple, and of one colour, green, red, 



brown, yellow, or even black. 



As this substance is generally collected for 

 the sake of its colour, the more decided tints are 

 commonly found in cabinets, but it occurs of 

 various hues. 



b. Striped with different colours, in conse- 



quence of a laminar structure. 



The Siberian green and red variety belongs 

 to this ; it also occurs of different tints of red 

 alternating, or of greys, or of other colours. The 

 latter are also enumerated among the siliceous 

 schists. 



