What is Ironstone ?
Ironstone is a sedimentary rock formed on the sea bed in the Jurassic period, 185 million years ago.
The iron-bearing minerals are siderite and chamosite, with an iron content in the stone around 30%.
The “Main Seam” was the one worked in the majority of Cleveland mines, at Eston this is as much as 15ft thick but thins down to 5ft as you move South.
The “Pecten” and “Avicula” seams are named after types of fossilised scallop shells found within, these can be seen on the beach at Staithes and in river at Grosmont.
The ironstone is deposited in a deep bowl centred on North Skelton, 400ft below sea level.
Ironstone rises rapidly and outcrops at surface, 400ft above sea level at Eston.
Figures : Cleveland iron and steel: background and 19th century history
Almond, Harrison, Harrison, Owen
British Steel Corporation 1979