IRISH MINERALS AND BUILDING STONES 2a 



larger extent in each of the counties of Northumberland, Durham, and 

 Staffordshire, and is clearly of commercial interest. 



The soft magnesium silicate. Steatite, a massive form of talc, occurs here 

 and there in good veins, but is often mixed with 

 harder minerals, which destroy its utility. At Crohy 

 Dteatite. Head, and Gartan, however, in the County of Done- 



gal, considerable and good beds occur among the 

 ancient metamorphic rocks. 



While Ireland cannot claim especial richness as a mineral country, she is 

 essentially a stone country, and quarries have been opened everywhere for 

 building purposes and for road-metal, even through the sands and gravels 

 of the plain. Naturally, limestone is the chief substance excavated ; and 

 the frequent deficiencies of the Irish roads are due to the general use of 

 Carboniferous limestone as a metalling. The country possess excellent 

 igneous rocks, which should be imported into all districts where they are 

 required. In this matter, the growing practice of England, and of many 

 foreign states, notably Saxony,* is strongly to be commended, seeing that 

 good roads are far more economical to mamtain than bad ones, and that they 

 give an impetus to activity and intercommunication such as no main line of 

 railway can bring about. In Ireland, far more than in England, the roads 

 perform the functions of branch lines — witness those numerous stations 

 named after roads, and situated miles away from the towns which they 

 are meant to serve. When the selection of proper road-metal is seriously 

 considered in rural districts in Ireland, the country itself will be fully able 

 to cope with the demand. 



The clays used for bricks have been mostly derived from the Glacial 

 drift-deposits, where these are not too highly charged; 

 p, with limestone debris. The Triassic clay of Kings- 



^ ' court has produced good results, while the carboni- 



ferous fire-clays are raised in connection with some of 

 the coalfields, notably near Dungannon. These ancient shales, when 

 crushed, yield bricks capable of resisting a high temperature, provided that 

 they are not too ferruginous. The Ordovician shales are similarly utilised 

 at Waterford. Numerous clays suitable for ordinary red and brown glazed 

 ware exist throughout the country. The clay of the Lagan valley near 

 Belfast, and that on the north side of the Ovoca at Arklow, are used for 

 terracotta. 



True porcelain-clay, or kaolin, does not appear to occur in Ireland, though 

 it might have been expected as a product of decay from the granite areas. 

 The materials mentioned under this head by Mr. Kinahan are really arti- 

 ficially crushed felspathic rocks, without the composition of true kaolin. 

 The famous pottery of Belleek, in County Fermanagh, was thus formerly 

 made from the crushed alkali-felspars of the granite on the north shore of 

 Lough Erne. The material used is still a felspar, but is imported. 



The diatomaceous earth which has accumulated in such purity near 



Toome, in County Antrim, where the Bann flows out 



Kieselguhr. of Lough Neagh, is now worked for various purposes, 



under the usual commercial name of " kieselguhr." 



Irish slates have suffered, from a business point of view, through the 



* See O. Hermann, " Steinbruchindustrie und S tein.br uchgeol ogie " (1899), p. 351, where 

 an analj'Sis is made of the Saxon highways, proving that the limestones and soft rocks that form 

 40 percent, of the surface of Saxony are nowhere employed upon the public roads. 



