22 GEOLOGY OF THE ISLE OF WIGHT 



Among other objects of interest along this Weal den 

 shore may be noticed a curious transformation which has 

 affected the surface of some of the shell limestones after 

 they were formed, which is known as cone-in-cone structure. 

 It has quite altered the outer layer of the rock, so that all 

 trace of the shells of which it consists is obliterated. Numer- 

 ous pieces of iron ore from various strata lie on the shore. 

 Through most of English history the Weald of Kent and 

 Sussex was the great iron-working district of England. 

 The ore from the Wealden strata was smelted by the 

 help of charcoal made from the woods that grew there, 

 and gave the district its name ; for Weald means " forest." 

 This industry gradually ceased, as the much larger supplies 

 of iron ore found near the coal in the mines of the North 

 of England came to be worked. Iron pyrites, sulphide of 

 iron in crystalline form, was formerly collected on the 

 Sandown shore, and sent to London for the manufacture 

 of sulphuric acid. This mineral is often found encrusting 

 fossil wood. It also occurs as rounded nodules (mostly 

 derived from the Lower Chalk) with a brown outer coat, 

 and often showing a beautiful radiated metallic structure, 

 when broken. (This form is called marcasite.) 



As we walk by the edge of the water, we shall see what 

 pretty stones lie along the beach. When wet with the 

 ripples many look like polished jewels. Some are agates, 

 bright purple and orange in colour, some clear translucent 

 chaldedony. We shall have more to say about these 

 later on. They do not come from the Wealden, but from 

 beds of flint gravel, and are washed along the shore. But 

 there are also jaspers from the Wealden. These are 

 opaque, generally red and yellow. There are also pieces 

 of variegated quartz, and other beautiful pebbles of 

 various mineral composition. These are stones from older 

 rocks, which have been washed down the Wealden rivers, 

 and buried in the Wealden strata, to be washed out again 

 after hundreds of thousands of years, and rolled about 

 on the shore on which we walk to-day. 



