Lamplugh (geology of IoM 1903 has
Ballaglass or Great Mona Mine.

Large sums of money were expended upon this trial of a small north-and-south lode discovered in the bed of Cornah River 1,050 yards E. of the high road from Ramsey to Laxey. The workings commenced about 1854; and in 1857 Sir W. W. Smyth reported that much spirit was being shown in driving the 10 and 24 fathom levels, on a vein with small portions of copper, zinc and lead, but too narrow to warrant much further outlay. In same year there is a record of 9 tons of lead ore and 8 tons of zinc ore to the credit of the mine in "Mineral Statistics," which appears to be the only return made from it. The mine was then suspended for some years, but restarted by the Great Mona Mining Co. in 1866, with no better success. In 1867, Smyth noted that a few stones of ore had been raised.; and in 1868, that the shaft was down to 50 fathoms, with no improvement. This appears to have been the depth attained when work was abandoned. The lode is said to have been nowhere more than 6 to 12 inches wide, and to have had an easterly underlie. A small uncrushed igneous dyke of peculiar character traverses an E.—W. joint or small fault in the slaty flags immediately to the westward of the mine (see p. 140), and must be intercepted by the lode. An intrusion of different character has been encountered in the workings, as shown by the fragments of sheared ‘greenstone’ contained in the spoil-heap.

Sounds as if speculation was very much hyped