MODE XI. JASPER. 99 



" Geognostic Situation. 



" It belongs to the floetz-trap rocks, and con- 

 stitutes, like wacken, the basis of amygdaloid. 



" Observations. 



" It is distinguished from wacken by its colour, 

 and the greater proportion of iron which enters 

 irito its composition. 



"2. The iron which it contains is very much 

 oxydised, whereas that in basalt is slightly oxyd- 

 ised."* 



MODE XI. JASPER. 



Texture, very fine grained and compact, some- Characters, 

 times rather earthy. 



Hardness, crystallie, sometimes only felsparic. 

 Fracture, conchoidal. Fragments, angular sharp. 



Weight, sometimes siderose, sometimes grani- 

 tose. 



Lustre, glistening, rising to shining, but some- 

 times dull. Opake; sometimes translucent on 

 the edges, but it then passes to jaspagate. 



The most frequent colour of jasper is the red, 

 which has been found to contain from 16 to 20 



* From the additions to Mr. Jameson's Mineralogy, ii. 603. 



ii 2 



