Geology
Leinster granite was formerly largely quarried at Dalkey, and the quarries at Ballyknockan, a remote village above the Kings River valley in Co. Wicklow (Hotels, Wicklow, Ireland), as well as numerous excavations south of the city, supply excellent stone which is brought by road to Dublin. The igneous dykes in the Ordovician strata are now selected for road-metal, especially the dolerites of Bohernabreena, Mount Seskin, and Rathdrum. The Cambrian Quartzite of Howth and Shankill also supplies good material. The, county of Wicklow uses various highly siliceous lavas and also selected dolerites. The boulder-clays furnish brick-days in many places. Iron-mining is now no longer carried on, though recent work has been done on the magnetite, lode at Ballard south of Wicklow (Bed and Breakfasts, Wicklow, Ireland) town ; but various veins were used for local smelting-works in the seventeenth century. Lead-ore lias been raised at Clontarf, Killiney, in the Glendalough district, and at Ballycorus near Dublin, and the smelt- ing-works established at Ballycorus were long carried on with imported ore. Casual veins of copper pyrites have been mined at Loughshinny in Co. Dublin and elsewhere, and copper is still procured from the great veins of pyritous ore in the Vale of Ovoca in Co. Wicklow (Holiday Apartments, Wicklow, Ireland). These lodes consist mainly of finely granular iron pyrites, developed in shaly Ordovician strata along the strike of tlie beds, and are mined as sulphur ores, supplying the material for sulphuric acid manufacture. The best known mines are. those of Ballymurtagh, Tigroney, and Cronebane. In the Ballymurtagh dig- gings, brown ochre is raised, resulting from the deep decay of the lodes of iron sulphide. 
Still more famous, as the probable source of the gold that was used so freely in prehistoric days in Ireland, are the alluvial gravels of the Aughrim district in Co. Wicklow (Self Catering, Wicklow, Ireland). The streams that descend northward on Woodenbridge bring down particles of gold, which may have been derived from the unprospected igneous ridge of Croghan Kinshela. At the close, of the eighteenth century, considerable workings were undertaken in the valley-floors, and a nugget weighing 22 oz. that was discovered in 1795 was at that date the, largest native specimen known. The higher benches of gravel do not seem to have been investigated