24 IRISH MINERALS AND BUILDING STONES. 



proximity of the enormous supplies of Llanberis and 



_. Ffestiniog, in N. Wales. A local use has, however, 



been found for many slates occurring in inland or 



western localities. The quarries in Ordovician strata 



in Clashnasmuth townland, six miles from Carrick-on-Suir, have a sound 



reputation, some of the material being selected, on account of its green 



colour, for special decorative effect. Similar slate is raised not far away in 



County Kilkenny, from quarries at Kilmoganny. Near Killaloe, again, 



roofing slates are raised. The firm tough slate of Valentia Island, in County 



Kerry, is suitable for flags and slabs, which are obtained there of an unusual 



size. Slates are also raised from the Carboniferous Slate series west of 



Clonakilty in County Cork. 



The fine-grained bedded sandstones of Upper Carboniferous age in 

 Ireland are at times extremely tough and durable. 

 -,, . The dark flags of south-west Clare, and the similar 



° ' slabs raised in County Kilkenny, and sold as " Carlow 



Flags," have been, in consequence, widely used for 

 paving. Good flagstones are also recorded from the Lough Allen area. 

 The best Irish sandstones for use in architectural work in towns, and 

 some of the finest in texture in the British Isles, occur 

 „ , , in the Carboniferous system in the Counties of Done- 



gal and Fermanagh. The stone of Mount Charles in 

 Donegal, though of course not so easily worked as 

 limestone, is capable of receiving a sharp edge, and of being used for 

 moulded work of a delicacy unusual in this class of material. While the 

 soft Triassic sandstones, like those of Scrabo, in County Down, are not 

 suitable for monumental work in the smoky atmosphere of towns, and 

 while much of the Old Red Sandstone of the south must be put aside on 

 account of its coarseness of grain, the Carboniferous sandstones may receive 

 more and more attention as time goes on, and may be found worthy of 

 export to the manufacturing cities of England. 



There is no lack of good grey Carboniferous limestone in the broad 

 central Irish area, and much has been done with this 

 Limestone and material, both for massive structures and for decora- 

 Marble, tion. The shaly varieties, black through included 

 mud-particles, and locally known as " calp," are to be 

 avoided for all but common walls, since they weather out unequally along 

 the planes of stratification. The opposite type, uniform and fine-grained, 

 is seen in the grey limestones of Roscommon, in which excellent carved work 

 has been effected, and which are practically marbles, utilised as building 

 stones. 



The Carboniferous limestones become occasionally dolomitic, the change 

 being, as usual, marked by the introduction of iron as well as magnesium. 

 The rock, in consequence, becomes brownish on oxidation, sometimes in 

 flecks and patches. This variegated colouration enhances the effect of 

 certain varieties, and makes them serviceable as ornamental marbles. 



The black marbles of Ireland have long been famous. They are Carboni- 

 ferous limestones coloured by a small percentage of graphitic carbon, and 

 have been quarried mostly near the cities of Galway (Menlo) and Kilkenny 

 (Archer's Grove). The Menlo rock provides pure black stone, while the 

 white sections of fossil brachiopods afford a striking feature amid the black 

 ground of the marble of Kilkenny. 



Other marbles that have achieved marked success for decorative work 



