This was a period of major economic development in Killarney, centering on the fortunes of two planter families, the Brownes (later Earls of Kenmare) and the Herberts of Muckross and Cahirnane. Both estates encouraged mineral exploration from the early 1700s, leading to mine operations at Ross Island and Muckross, and to trials at nearby Cahirnane, for copper, lead and possibly silver. This period also saw iron smelting ventures in Killarney, taking advantage of abundant wood fuel and local sources of bog iron. Many rock quarries were also opened, extracting limestone for agricultural use and 'marble' for cut stone.

Old Iron furnace, Derrycunnihy, Killarney (Jonathan Fisher 1789)

The earliest record of mining on the Kenmare estate dates to 1707 when John Asgill raised four ton of lead ore on Ross Island. In 1726, Joseph Bacon of Castlelough obtained a 21 year agreement to work this mine, with little apparent success as the lease was surrendered in 1731. The next phase of mining here dates to 1754 when Thomas Herbert came to an arrangement with the Kenmare family. In 1758, the traveller Richard Pococke visited Ross Island and observed that '...there are very considerably copper mines, which have brought a great profit, but the vein is grown very small'. Records point to management difficulties at this time, and to problems caused by lake flooding and careless mining. Finally, mining under the direction of one Barnoff is recorded at Ross Island in 1785, however there are no details.

Trials for lead ore at Cahirnane (Rudolf Raspe 1793)

Other mining attempts in this period include the discovery in 1761 of a metallic bed containing lead ore on the Herbert lands at Cahirnane. A trial shaft was sunk and one ton of ore raised. The Herberts extended this trial in 1794 under the direction of Rudolf Raspe, wasting a great deal of money on what became known as the 'Copper Folly'. Lead ore was also discovered at Coolclogher near the river Flesk, but not in sufficient quantity to mine.