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Geology Matters No. 7
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IRELITHOS
Gerry Stanley

The OPW has responsibility for the maintenance and preservation of buildings belonging to the State and National Monuments. Many, if not all, of the buildings and monuments have as their primary construction material natural stone. Should a building or monument be in such a poor state of repair that particular stone elements need to be replaced then it is essential that (in decreasing order of importance):

  • Replacement stone is sourced that comes from the original source.
    OR
  • A stone of the same type is sourced.
    OR
  • A suitable substitute is located.

The architectural archive contains information on the stone used in many of the buildings under the care of the OPW. Another valuable source of information is the “Practical Geology and Ancient Architecture of Ireland” by Wilkinson. However, many buildings do not have any papers recording the type of stone used in their construction.

The GSI maintains a Directory of active pits, quarries and mines. In addition, the GSI has over its 160 years collected and maintained information on rock types and quarries through its extensive archive of field observations.

Many rock types are sufficiently distinctive that they can be identified by simple observation. In other cases it may require additional investigation. A range of possibilities exist, such as:


  • Staining (certain minerals are highlighted by these techniques).
  • Thin section examination (petrography).
  • Palaeontology (fossils).
  • Geochemistry (having the rock analysed to reveal its chemical composition).

Once a rock type for a building or monument has been identified it will be a simple matter to identify where this rock type occurs in the country as a whole and more importantly in proximity to the building or monument through a GIS application.

The project will create a database of the stone used in the construction of the buildings and monuments selected for study. The work will involve the collation of existing information, the collection of permitted samples from the buildings and monuments, the description of the samples, other relevant test work, the development of computer databases, and the documentation of the current state of each site.

A view of the Casino in Marino in Dublin.  The principal stone used in this building is Portland Stone – a Jurassic oolitic limestone from the south of England.
A view of the Casino in Marino in Dublin. The principal stone used in this building is Portland Stone – a Jurassic oolitic limestone from the south of England.


Some examples of the work carried out are displayed in the diagrams attached to this article.

Quarries (Calp limestone) in the Crumlin – Dolphin’s Barn area of Dublin marked on GSI’s 1:10,560 field sheets.
Quarries (Calp limestone) in the Crumlin – Dolphin’s Barn area of Dublin marked on GSI’s 1:10,560 field sheets.

The Crumlin – Dolphins barn area today.
The Crumlin – Dolphins barn area today.

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