John Marley (11 November 1823 – 4 April 1891) was an English mining engineer from Darlington who together with ironmaster John Vaughan made the "commercial discovery"[1] of the Cleveland Ironstone Formation, the basis of the wealth of their company Bolckow Vaughan and the industrial growth of Middlesbrough.

He ended his career as a wealthy independent mine-owner and president of the North of England Institute of Mining and Mechanical Engineers (NEIMME).

[4] The existence of iron in the Cleveland hills was in fact well known, possibly since ancient times[5] and certainly since at least 1811, as repeated attempts had been made to sell it, but without success.

[9] By 1881, John Marley was living at Thornfield House, Darlington with his wife Sarah, four daughters, Caroline, Florence, Ethel and Isabel, and a son, Hugh.

Two Ammonite zones (rock layers identified by particular fossils) are (largely) included: those indexed by Pleuroceras spinatum and Amaltheus margaritatus.

They discovered seams of the ironstone running from the North Yorkshire coast at Staithes inland to the Eston Hills, outcropping at the surface.

This find was swiftly exploited, and Middlesbrough grew very rapidly to support the new ironworks developed by Bolckow Vaughan and others in the area.

[15] Marley is recorded as doubting "whether the Romans or the Monks [of Rievaulx] ever smelted any part of the main bed of ironstone, which has in recent years proved such a source of wealth to the North, because in the various remains of slag and refuse left by them in Bilsdale, Bransdale, Rosedale, Furnace House in Fryupdale, Rievaulx Abbey, and other places, no traces of the main seam of ironstone have been found, although 'dogger band' (or thin clay bands of ironstone) and 'nodules' have been so found along with the charcoal and slag.

"[17] The legend about the rabbit-hole did have some basis in reality: the many rabbit and fox holes provided the prospecting geologists with samples of the underlying rock (away from surface exposures of the geology at natural cliffs) at intervals along the ironstone outcrop.

Marley stated "I need scarcely say that, having once found this bed, we had no difficulty in following the outcrop in going westward, without any boring, as the rabbit and fox holes therein were plentiful as we went.

[1] In 1857, Marley published a paper in the Transactions of the Institution of Mining Engineers on the Cleveland Ironstone, which begins: "To the members of this Institute, this ironstone cannot but be an interesting subject, whether they be mining engineers, coal owners, iron masters, or simply a part of the public personally disinterested, as I believe that nothing has been discovered, within the last twenty years, having so direct an influence on the landed, railway, and mineral wealth, in the North of England, on the South Durham coal field, and on the iron trade generally, as the discovery and application of this large ironstone district.