NOME VIII. KOLLANITE. 101 



to which it sometimes passes, according to Mr. 

 Kirwan, it is often accidentally impregnated 

 with jasper. 



These pebbles are often found detached, and 

 of a particular beauty ; which, wanting however 

 the delicacy of some agates, resembles that of a 

 rustic girl when compared with the elegance of 

 high life. Some present circles and shades of 

 various tints of brown, approaching to the 

 Egyptian pebbles ; others, various concentric 

 lines of yellow and brown, yellow red and black; 

 and others display a centre of red or crimson, 

 with concentric bands of yellow and olive green. 

 There is also a rare kind called the zebra, from 

 its regular black bands upon a white ground. 

 If we believe Dr. Woodward*, who made a very 

 large collection of English pebbles, fine agates 

 have been found near Gaddesden, in Hertford- 

 shire, one of the boundaries of the pudding-- 

 stone ; where have also recently been discovered 

 some fine flints with purple illinitions, like land- 

 scapes, perhaps tinctured with manganesef. 

 That industrious author informs us that the Kol- 

 lanite is common about Berkhamstead, in Hert- 



* Nat. Hist, of English fossils. 



f Collmi observes, p. 146, that agates are easily detached from 

 the rock, because each is enveloped in iron ochre. This remark 

 applies to many kollanites. 



