Aggregates or construction materials quite literally form the building blocks of modern industrial society. Construction projects rely on locally available sources of aggregate for concrete production and our entire transportation network would not exist without the input of local materials. In addition, aggregate products are also used in water treatment plants and drainage/sewerage systems and specialised aggregates are necessary for the chemical industry.
Aggregates in Northern Ireland
As a result of its varied geology, Northern Ireland has a diverse aggregates base upon which the construction industry has developed. In 2004, there were 137 active quarries and pits extracting material primarily for the local market. A total of 1,584 people were employed in the industry and it produced 25.7 Mt of material valued at £88.8 million. The primary products extracted include sand and gravel, basalt, sandstone (including greywacke) and limestone. Most quarries are operated by family-owned businesses, but a number are larger and part of multi-national companies.
Sand and Gravel
Sand and gravel deposits formed at the end of the last ice age between 10,000 to 13,000 years ago. As the glaciers began to melt, the material they had eroded was transported into large glacial lakes where it was deposited to form the typically well-sorted fluvio-glacial deposits that characterise the Northern Ireland landscape today. In 2004, Northern Ireland produced over 5 Mt of sand and gravel primarily for use in the building industry.
Limestone deposition occurred at three main times during Northern Ireland’s geological past. The oldest Dalradian limestones have all been metamorphosed to marble and may have dimension stone potential. The most widespread limestones formed during the Lower Carboniferous in Co. Fermanagh. The youngest limestones are a special variety known as chalk and produce a very high purity product. Limestone is quarried for uses in the production of concrete as well as the agricultural industry. Minor occurrences of high magnesium (dolomitic) limestone are quarried to counteract magnesium deficiencies in livestock. In 2004 over 5.6 Mt of limestone was extracted.
The basalts of the Antrim Lava Group are worked for their aggregate potential, particularly within the road building industry. As a typically uniform, finegrained, hard, dark rock it has many of the properties necessary for use in the transportation network. In 2004 over 6.8 Mt of basalt was produced from wellsituated quarries, mostly in Co. Antrim.
Sandstone includes the Silurian greywackes (or gritstone) of Counties Armagh and Down. These have high polished stone and aggregate abrasion values, making them a particularly good source of wearing course aggregate. In 2004 Northern Ireland produced over 6.9Mt of sandstone mostly for use in the roads industry.
A number of other commodities are extracted from quarries in Northern Ireland, including granite from the Mourne Mountains in Co. Down, schist from the Mesoproterozoic in Co. Tyrone and slate from the Lower Palaeozoic rocks of Counties Armagh and Down.
Published: 8th December 2009
Last Updated: 25th November 2011