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Limestone geology,Muckross Lake 'And richest marble swells the pregnant ground, while deep beneath the golden ore is found' (Patrick O'Kelly 1791) The metal mines of Killarney lie on the junction of two great rock
formations, separated by a geological fault zone. The mountains to the
south and west are comprised of Old Red Sandstone rocks laid down some
395-345 million years ago in the Devonian Age. To the north, beyond
Killarney town, the undulating lowlands are formed by rocks belonging to
the younger Carboniferous period. These are mostly comprised of
different types of limestone that are well exposed along the shores of
Muckross Lake and Lough Leane. They are sedimentary rocks laid down at a
time (345-295 million years ago) when the south of Ireland was covered
by a warm sea. This limestone is composed of calcium carbonate formed
when the skeletons of marine organisms and fragments of coral settled on
the ocean floor. The Carboniferous period came to an end about 295 million years ago when great continental land masses collided and mountains rose over much of western Europe. The enormous stresses of this Hercynian period folded and fractured the Devonian and Carboniferous rocks around Killarney. Water trapped in these rocks was super-heated and this dissolved the low concentrations of copper, lead and zinc that were also present. These metals were subsequently deposited in a concentrated form through certain limestone beds or else as veins filling rock fractures. Metallic ore deposits are known to have been mined at four locations in the Killarney area. The two richest ore-bodies are at Ross Island and on the Muckross Peninsula, with smaller occurrences on Crow Island and nearby Cahirnane. All four mineral deposits occur within the lower Carboniferous limestone and contain varying amounts of copper, lead, zinc, silver and cobalt. Iron is also found around Killarney, mostly in the form of bog ores in the mountain landscape to the south.
Limestone with copper minerals, Ross
Island
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