Largest among the Iron Mines of Eskdale is Nab Gill Mine, whose levels were driven from the ravine of Nab Gill above Boot. While all the mines in the area were abandoned by the mid-1880s, Nab Gill Mine saw sporadic reopening efforts, notably in 1909 and again in 1917. Although none of these mines proved commercially successful, their existence paved the way for the construction of the charming Ravenglass & Eskdale Railway, originally built for transporting iron ore.

In 1909, Messrs J.B. Hardie and J. Laird reopened the bottom level of Nab Gill Mine, but the amount of ore obtained was insufficient to sustain the venture. They abandoned the mine in 1912. The last attempt to revive operations was in 1917 when four men worked the bottom level for about a year, yielding very small tonnages.

The first documented mention of this site dates back to 1845 when Messrs S and J Lindow leased the area covering Ban Garth and Nab Gill. However, by 1854, they shifted their focus to Ban Garth, indicating a loss of interest in Nab Gill Mine. By 1871, Mr. Faithful Cookson sub-let the site to Whitehaven Iron Mines Ltd.

Nab Gill Mine derived its name from a distinctive cleft on the vein of hematite near the summit of the valley side. The site is characterized by extensive remains, including massive spoil heaps, the remnants of multiple adits, inclined planes, and a track system. The ruins of the mine offices sit atop a loading platform above the turf-covered remains of Boot railway station and sidings. At a specific location, approximately over 350 meters, the ground flattens considerably, incorporating collapsed areas from underground workings, small-scale surface workings or prospecting trenches, and two ventilation shafts. Surface activity appears to be limited to about NY 172 017.

1878-1881 Whitehaven Iron Mining Co. 1909-1912 Eskdale Mining Co. 1916-1918 Nab Ghyll Iron Mines