A SEASIDE RAMBLE 213 



hood of the undercliff, and we find on all sides an 

 abundance of iron pyrites, in the form of round 

 nodules about the size of tennis balls. 



Not unfrequently do the visitors to this spot persist 

 in calling them ' thunderbolts,' while others who find 

 bright samples believe they have found a gold mine. 

 We break a specimen open, and it shows a beautiful 

 gold-like sheen, with radiations from its centre to its 

 entire surface a veritable hidden beauty. These 

 nodules are used for staining leather ; but as both 

 iron and sulphur can be obtained pure or nearly so, 

 this mineral is of little value. Instead of being 

 ' thunderbolts,' they are formed in most of our chalk 

 cliffs. 



A much rarer and more beautiful variety of iron 

 pyrites, which we shall find presently, is known as 

 marcasite, or spear pyrites. Each crystal is formed 

 like a spear head. A number of these spear-head 

 crystals sticking out in all directions, and all glisten- 

 ing like gold, makes a specimen worthy of a place in 

 a geological cabinet. Still we must not despise our 

 more common form, but give it also a place side by 

 side with its rarer cousin. It will enhance the edu- 

 cational value of both specimens if we leave them in 

 the surrounding block of chalk, exposing the main 

 portions. The chalk may be cut to a convenient 

 size and shape. Thus the nature of the matrix can 

 be seen at a glance. 



In opening up this large block of chalk we find a 

 vein of calc spar, by following which we are led to 



