IRON OF CORNWALL AND DEVON. 427 



The South "Wales iron is chiefly in the Gannister beds. In the 

 Cleveland district of Yorkshire, extending south of the river Tees, 

 the middle lias contains important beds of clay ironstone. 



In the north-west of Lincolnshire, a similar ironstone occurs in 

 the lower part of the lower Lias ; and in Northamptonshire the 

 Northampton sands, corresponding to the lower part of the inferior 

 oolite, have yielded rich deposits of iron ore about Wellingborough, 

 Crauford, and Woodford. 



Iron in Cornwall Most of the iron in Cornwall occurs between 

 Padstow on the north and the neighbourhood of St. Austell on the 

 south. Among the more important of these lodes are the Pawton 

 mines near Padstow. The ore is partly red hematite mixed with 

 limonite and spathose carbonate. The Perran lode has similar ore, 

 but has a direction 35 north of west. 



Many other localities in Cornwall are known to yield good ores of 

 iron, and among the more important are Boscarne, west of Bodmin ; 

 Tregorne, west of Mulberry Hill, and the neighbourhood of Gram- 

 pound, where magnetic ore occurs. 



The iron lodes of Cornwall mostly run to the west of north, and 

 contain hematite or limonite. An important mine occurs at Lost- 

 withiel, and extends for if miles; the ore is chiefly the hydrous 

 oxide termed Goethite. Near to the surface the carbonate of iron is 

 altered into limonite. The ore yields thirty to fifty per cent, of 

 metal. 



Iron in Devonshire. The Hay tor iron mines on the eastern 

 border of Dartmoor are an example of the occurrence of thick beds of 

 magnetite, interstratified with altered shales and sandstones of Car- 

 boniferous age. The rock near the iron ore is always charged with 

 hornblende, and sometimes almost made up of actinolite. 



The beds of iron ore are, according to Dr. Le Neve Foster, ten feet, 

 fourteen feet, and six feet thick in three of the four beds. The 

 strike of the beds is south-east. The iron ore is thought to have 

 been originally in a condition like that of Cleveland ore, and to have 

 been subsequently altered into magnetite. Near the surface the 

 magnetite is converted into ochre by atmospheric decomposition. 

 Actinolite and garnets almost invariably accompany deposits of 

 magnetite. 1 



Magnetite iron ore worked at Haytor, near Islington, is a com- 

 pact black granular substance. Iron ore occurs at Smallacombe in the 

 form of limonite. Other lodes of brown hematite are found at 

 Hennock, Buckfastleigh, and North Moulton. At the Frank Mills 

 lead mine the lead ore is succeeded by carbonate of iron containing a 

 large amount of manganese. 



Red hematite and limonite are found in the Plymouth limestone, 

 near Brixham ; the ore is mostly compact, and includes some kidney 

 ore ; on analysis it yields from forty-four to sixty-three per cent, of 

 metal. 



Somersetshire Iron Ores. In Somersetshire iron ores occur at 



1 Dr. Le Neve Foster on Haytor Iron Mine. Q. J. G. S., vol. xxxi. p. 28. 



