Geological Relations of the East of Ireland. 203 
Luganure. The quartz mass of Glendalough vein abounds in 
occasional cavities, sometimes lined with quartz crystals, and more 
or less filled with clay, iron ochre, or white lead ore, which latter 
substance occupies also fissures in the quartz. The vein bears like- 
wise galena, copper pyrites, sparry iron ore, and heavy spar, which 
appear irregularly disseminated through the mass, or forming dis- 
continuous ribs and strings. Traces of blende and iron pyrites 
also occur. On the south side of the waterfall it consists princi- 
pally of quartz incorporated more or less with sparry iron ore, 
containing massive and disseminated copper pyrites, of good 
quality. 
The lead ore of this vein produces 70 per cent., and the copper 
ore from 10 to 15 per cent, of metal; but the galena was obtained 
in a continuous mass in one part only. It was found, to the 
amount of about a ton in weight, near the surface, where the vein 
first enters the mica slate, and it was there I discovered, in blasting, 
those fragments of mica slate imbedded and firmly consolidated with 
the veinstone, of which fig. 5, PL 13. is a representation. The 
surface here depicted is about four feet wide, which I left untouch- 
ed, for the gratification of future visitants. The very position of 
these fragments bespeaks disturbance, for scarcely any two of them 
perfectly agree in the relative disposition of the laminae. To a 
similar disturbance may also be ascribed the occurrence of the 
granite fragments, already mentioned, in the mass of Luganure 
vein. 
§ 96. In the waterfall, at the head of Glendalough, is a vein of 
quartz about one foot in width, which abounds in cavities lined 
with quartz crystals, and partly occupied with iron ochre and some 
disseminated copper pyrites. This vein has regular smooth walls, 
and ranges in the granite 30° west of north and east of south, 
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