288 Scientific Proceedings, Royal Dublin Society. 



Carboniferous Limestone is divided into Lower Shaly Limestone- 

 Fenistella Limestone, and Calp ; the latter in part of theBurren type. 

 Above and below the Fenestella Limestone are well-marked cherty 

 zones, and below both of these, especially the first, mineral accu- 

 mulations occur. Some rich pockets and shoots were found and 

 worked out prior to 1850 ; while since then lead has been found 

 in a few places, but the extent of the deposits have not been proved. 

 According to Lewis (1837), "there are indications of a valuable- 

 mineral ore near Tory Hill; " no trials, however, seem to have been 

 made thereabouts. 



In the Carboniferous Sandstone and the Ordovicians a few small 

 veins with copper have been found, but not sufficient to mako 

 mines. 



Large amethysts and cairngorms are found near Shanid Castle 

 and Foynes. 



Londonderry. 



At the east of the county, extending in from the Co. Antrim, 

 there is a tract of Eocene (?) Doleryte, which overlies the Cretaceous, 

 Jurassic, Triassic, and Carboniferous rocks. To the northward the 

 rocks of these older formations, except the Carboniferous, form 

 more or less narrow, continuous, successive strips, margining the 

 Doleryte ; but southward the latter more or less overlaps them 

 all. The Carboniferous rocks are for the most part of the North of 

 Ireland " Calp type ; " but in places there are good limestones, 

 and in others sandstones and conglomerates of the Lower Carbonife- 

 rous types. The Carboniferous rocks were evidently accumulated 

 in valleys in the older Metamorphic rocks, which occupy the rest 

 of the area, and therefrom into the counties of Donegal and Tyrone. 

 They are probably of Crdovician age. With the Metamorphic 

 rocks are associated intrudes of Grranyte. 



In the Eocene (?) Diorytes, as in the Co. Antrim, there are 

 beds of iron-ore ; but not as numerous or valuable. In the Calp 

 shales near Draperstown are clay-iron-stone bands and nodules : 

 worked by Rennie, and smelted in the valley of the Moyola, prior 

 to 1640. This Iron Master also mined hematite and limonite in 

 the Ordovician and Grranyte rocks. Between 1860 and 1870 

 openings were made on these lodes, but no permanent work done. 



