Special reports on the mineral resources of Great Britain . among them Restormel, had been in operation forsome time. The value of the iron-ore is, however, insignificantin comparison with that of the ores of tin and of copper. The development of the mines is indicated by the 1855 and 1865 this fluctuated from 19,000 to 55,000 tonsper annum; it fell in 1867 to about 4,600 tons, but rose in 1874to 45,000, then fell again to a few thousand tons a year. Theimportation of the cheap Spanish ores led to the closing of Cornishmines. A few, restarting for short periods, have vielded sin
Special reports on the mineral resources of Great Britain . among them Restormel, had been in operation forsome time. The value of the iron-ore is, however, insignificantin comparison with that of the ores of tin and of copper. The development of the mines is indicated by the 1855 and 1865 this fluctuated from 19,000 to 55,000 tonsper annum; it fell in 1867 to about 4,600 tons, but rose in 1874to 45,000, then fell again to a few thousand tons a year. Theimportation of the cheap Spanish ores led to the closing of Cornishmines. A few, restarting for short periods, have vielded since1884 about 3,000 tons. The principal source of iron-ore is the Great Perran Lode, whichlies a few miles soulh of Newquay and extends from the coastinland for a distance of 4 miles (Fig. 7, p. 57). On this lode are ^ Rept. on Geology of Cornwall, Devon, and West Somerset {), 1839, p. 617. Geol. CORNWALL 51 situated tlie following mines: (1) Gravel Hill. (2) Mount andTrebisken, (3) Treamble, (4) Great Eetallack, (5) Duchy Peru^and (6) 58 UNBEDDED IRON ORES Nearly all the other lodes lie arouuJ the St. Austell granite-mass and principally between Wadebridge and St. Austell(Fig. T, p. 57). Upon them from west to east the following mineshave been worked: (7) Indian Queen, (8) Wheal Edith, (9) PitsMingle, (10) Pawton, (11) Tower Consols, (12) Coidvreath,(13) Lanjew, (14) Colbiggan, (15) Retire and Wheal James,(16) Woodley, (17) Nanstallon, (18) Boscarne, (19) Ruby,(20) Treliry, (21) Restormel, (22) Bodinnick, and (23) SouthTerras. The remaining mines are scattered, but lie mainly inWestern Cornwall, between Truro and Helston. The principalare: (24) Wheal Falmouth and Wheal Sperries, and (25)Constantine or Brogdens. Both the anhydrous oxides of iron: magnetite (Ye^iJj andhaematite (FCgOg), occur in Cornwall. Magnetite forms a con-stituent of the basic igneous rocks or greenstones and of thelavas, but not generally in sufficient quantity to be worked asan ore. Ex
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