Introduction

Loughshinny is a small fishing village outside of Dublin city, in the surrounding countryside of county Dublin. This small village hosts some truly excellent examples of folding as well as other geological features. The examples are text book quality, and can be seen in some international Geology text books. As well as folds several faults can be found in the area, some of these faults played host to copper mineralization, this is where the “copper mine fault” gets its name. Loughshinny was a once important source of copper.



Geology

The sedimentary beds in Loughshinny where folded almost 325 million years ago, during the Lower Carboniferous due to displacement from a major fault. The original beds where deposited in a basin. At the time the area would have been similar in conditions to a tropical area of today. The folds developed in 300 meter think beds of thinly bedded limestone turbidities and black shale. The more northerly you move at Loughshinny, the deeper the folds where formed, this is very important for mineral deposits and will be discussed in the next section. The resulting deformation and compression formed chevron type flexural slip folds. The folds where brought to the surface by uplift.

Mineralogy

When the folds where forming, small cracks opened up in the rock and infilling hydrothermal fluids deposited calcite. The calcite is massive, and rarely forms crystals. Crystals are very small when they do occur and are hexagonal. With the folds which formed deeper quartz was deposited, this highly altered the mudstone bedrock. The quartz crystals occur in druses and the crystal can vary in size from a few mm to a little over 1cm. They are stubby and are rarely double terminated. Oddly in “The Industrial Resources of Ireland” it is remarked “In the cliff, on the sea shore, near the copper mine of Lough Shinny, is a large body of fine crystals, where a boat may get near to be loaded, and some of them may be quarried large.”. In unaltered mudstone small specks of pyrite can also be found though they are quite poor.





The faults in Loughshinny played host to the copper mineralization. The fault allowed hydrothermal fluids to deposit chalcopyrite. It is recorded to have occurred in three veins. The copper mine fault is the main fault in the area, and gets its name for obvious reasons.

Mining History

Mining in Loughshinny began before 1770, when the mining began a tunnel was cut in 300 yards. Copper was raised in 1772 and the mine was abandoned until 1785 when more ore was found and exported to Swansea, in Wales, it is recorded in The Literary Panorama of 1807 that in Swansea, 36 tons of Loughshinny ore sold at prices from £l6. 9s.6d. To £23. 18s. “At Lough Shinny, near Rush, three veins occur, on which extensive workings have been made, and a good deal of ore raised from time to time, but the operations do not appear to be continuously carried on.” The mining was renewed several times, probably due to the increase in the price of copper, "and a copper mine, formerly worked here, has been recently inspected, with the object of ascertaining the propriety of applying more extensive capital and improved machinery to its productions."

The mine finally closed in 1845, and in 1847 the machinery used in the mine was auctioned off. Today the adit can still be seen, and it appears to be deep, and to have collapsed at some point. It is not advisable to go into the adit as it is quite dangerous. There is little or no other evidence that mining went on here, and if there was it has long since gone. This is a tendency of Irish mine sites!

Bibliography

http://www.loughshinnyvillage.com/intro.htm

http://www.mhti.com/mines_in_ireland_files/loughshinny.htm

The History of the County of Dublin, By John D'Alton, Published by Hodges and Smith, 1838

The Industrial Resources of Ireland, By Robert Kane, Published by Hodges and Smith,
1845

Ireland: Industrial and Agricultural, By Ireland Dept. of Agriculture and Technical Instruction, William P. Coyne, Published by Browne and Nolan, limited, 1902

Statistical Survey of the County Dublin, with Observations on the Means of Improvement: With Observations on the Means of Improvement; Draw Up for the Consideration, and by Order of the Dublin Society, By Joseph Archer, Royal Dublin Society, Published by Printed by Graisberry & Campbell, 1801

The Literary Panorama, By Charles Taylor, Published by s.n., 1807, Item notes: v. 2 (1807)

I would also like to say a huge thank you to Daniel Russell for his help on this article.

By Stephen Callaghan

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