From medieval times Rockingham Forest has been at the centre of iron making , the ores were reduced to metal by smelting with wood charcoal sourced from the forest, this hit its peak in the 17th century.
Already at this time bans had been put into place due to the destruction caused to the forests, it was said that mature trees could not be touched any more to preserve what was left, luckily the smelting with wood charcoal required renewable wood which the local forests had.
The process of inland forges carried on until the 20th century. Rockingham castle which occupies a commanding position on the oolitic escarpment, in which so much mineral wealth lies buried dates from Norman times and is said to have been built to protect the inland forges.
Northamptonshire itself supplied ore to Derbyshire, Nottinghamshire, South Yorkshire, South Wales, and it also supplied ore to the furnaces in the ore field itself. The Marlstone ore of Leicestershire went exclusively to the ironworks of Derbyshire and Nottinghamshire.
The first mention of any of the Northamptonshire mines was at the great exhibition of 1851, when samples of ironstone from various parts of Britain was shown, including specimens from the estate of Colonel Arbuthnot at Woodford, near Thrapston, Northamptonshire.
Only a small proportion of midlands ore emanated from mines. Mining as opposed to surface mines was rather rare and never a common practice in the ironstone fields, although mining did take place from very early days. This worked very well as alternative to removing heavy cover due to the quickness at entering the bed of iron sandstone instead of stripping whole areas. All of the mining was done from an adit driven into the hillside accommodating narrow gauge tracks, and were worked by “pillar and stall”. Pillars are left in the galleries to support the roof. The robbing of pillars still took place even when mechanical mining had advanced greatly forward, this was because large amounts of ore could be won by removing the pillars and leaving a forest of props behind. When all the pillars had been removed the miners would use a Sylvester (http://www.rrcpc.org.uk/newsletters/NL_V38_N2_A1.htm) , the best example of this left today is in Cranford where this surface damage can still be seen.
The 1951 effect of the act was that all ironstone workings from that date were restored after extraction, prior to this it was only mandatory if the lease stated so. For the industrial archaeologist they will usually find more remains searching the older surface mines.