IRISH rocks, hard though it is to imagine, were once a political issue. The Geological Survey of Ireland (GSI), now celebrating its 150th birthday, was once expected to reveal enormous resources of coal and precious minerals - and when it failed to do so by early this century, nationalists suspected perfidious Albion of the worst.
Sinn Fein became convinced that the GSI, set up by a British government, was part of a conspiracy to prevent undiscovered Irish coalfields from competing with those in Britain. The First Dail even brought over a Belgian geologist to report on the Slieveardagh coalfield and established a Commission of Inquiry into the Resources and Industries of Ireland.
Although nationalist fervour failed to discover coal in economic measures, the myth lived on that the GSI was not to be, trusted.
When Fianna Fail came to power, the new Minister for Industry and Commerce, Sean Lemass, insisted in a speech in 1933 that "we have large coal areas" but "we have found the geological reports prepared by the British government to be most unreliable, and I think it fair to assume that they were deliberately made so in order to prevent development in those directions."
Some 32 years later, Lemass as Taoiseach opened the Tynagh lead and zinc mine, one of the world's richest, and inaugurated a period of mineral exploration and exploitation which even Sinn Fein could hardly have dreamed of. Between 1965 and 1973 the value of the gross output from Ireland's mines increased from £800,000 to £27 million.
But as this splendid record of the GSI's turbulent history shows, the real villains of the mystery of Ireland's hidden mineral wealth were the native governments, which shamefully neglected the Survey in the early years of independence and almost killed it off.
The mapping of Ireland's rocks took from 1845, when the GSI was set up, until 1887. Originally it had been estimated that it would take 10 years and cost £15,000; but it was a miracle that it was ever completed when the minuscule size of the staff, their appalling conditions in the field and low pay are taken into account.
The heroic feats of these pioneers tramping the hills and valleys of Ireland are grippingly recounted by the author, for whom it is clearly a labour of love.
The intriguing "scandal of the Dingle Beds" and the "mystery" of the Blackwater at Cappoquin have elements of a detective story - but then geology is all about solving the puzzles of the Earth's crust, with only the rocks and their fossils for witnesses to millions of years of upheaval.
The GSI itself is a case study in Victorian intrigues as it moved from the Custom House to Stephen's Green and then to Hume St and acquired - and shed - various political masters.
For a golden period, its famous collections of rocks and fossils were displayed in the National Museum and the Curved Gallery joining Leinster House to the Natural History Museum.
The installation of the Dail meant that the fossils had to make place for the TDs and their staffs, so the collections were banished to packing cases in the basement of Hume Street for the next 50 years.
The revival of the GSI in the 1960s and 1970s under directors Murrough O'Brien and the South African, Cyril Williams, and the move to the present impressive home in Beggar's Bush mark the restoration of the Survey to its rightful place - of course, the discovery of Ireland's valuable mineral wealth contributed greatly to the GSI's rehabilitation.
The foreign prospectors who flocked to these shores came to value the work done by the 19th century geologists who had, unearthed the clues to the riches underground for those who had eyes to see.
Sinn Fein's instinct about mineral wealth waiting to be exploited turned out to be right, even if it was not to be coal.
The GSI in its early days may have been too oriented towards "pure geology" and less mindful of applied "economic geology", but this defect pales compared with the neglect of the GSI by the successors of Sinn Fein from 1922 until 1952.
