I recently experimented using a compass, firstly i placed a plastic wheelie bin well away from any metal objects, i then placed first a piece of rock taken from the great whinn sill at High force in upper teesdale on top of the bin. Then i approached the bin with the compass from about 3 metres, by the time i had placed the compass on top of the rock it had been deflected by 70-80 degrees.
Irepeated this proscess with similer sized pieces of rock my findings below.
Results
Whinn sill deflected 70-80 degrees ( High force)
Laverkiite deflected 20 degrees ( Staithes sea wall )
Coldberry ( Cleveland dyke ) 40-60 degrees
Stainton quarry Middlesbrough ( Cleveland dyke ) This i repeated 3 times 70- 180 degrees.
Irepeated this proscess with similer sized pieces of rock my findings below.
Results
Whinn sill deflected 70-80 degrees ( High force)
Laverkiite deflected 20 degrees ( Staithes sea wall )
Coldberry ( Cleveland dyke ) 40-60 degrees