KiNAHAN — Quartz, Quartz-Rock, and Quartzite. 581 



succeeded in being able to lay down any law by which one could be 

 distinctly separated from the other. Both are more or less clastic, 

 both have linings like bedding, and both may occur as intrudes or pro- 

 trudes, or between the layers of stratification, the "lay and lay" of 

 the miner, or as dykes and veins. 



As far as my knowledge goes Maculloch, the eminent Scotch 

 Petrologist, was a pioneer in separating quartzite from quartz-rock. 

 To my mind Scotchmen ought to be proud of him as the first observer 

 who had any idea of the classification of rocks. On the Continent 

 €otta and others separated quartz-rock from quartzite, calling the 

 first Greissen. At home "Wylie seems to have been the first to sepa- 

 rate quartz-rock from quartzite.^ He was subsequently followed by 

 John Kelly and Jukes, and after that by myself. I was led to my con- 

 clusions by the study during some twenty years of the silicious rocks 

 in different places in Leinster, Munster, and Connaught. In a recent 

 most interesting and learned Paper by Professor Sollas the old theory 

 as to the origin of the quartz-rock has been again put forward, that 

 is, that they are only altered or silicified ordinary sandstones and grits. 

 But in support of his statement he has not mentioned any one fact 

 hitherto unknown. That quartz-rock masses are in part, at least, 

 clastic ; that they have nearly always a lining or false bedding, and that 

 they occur as protrudes or intrudes, are all facts that were previously 

 known. Furthermore, it was also known and recorded, that some un- 

 altered arenaceous accumulations have very similar characters. Take, 

 as examples, the irregular masses of sandstone in the Cratloe Hills, 

 South Clare ; the so-called porphyries in the slate series of Killaloe, 

 counties Clare and Tipperary ; the protrudes of grits in the Slieve 

 Phelim district, county Tipperary ; the protrudes of grits in the 

 slate at KHcavan, county "Wicklow, and other protrudes mentioned in 

 the "Economic Geology of Ireland."^ These were recorded before the 

 writer imagined that the old theory for the genesis of quartz-rock 

 would ever be reproduced. All these arenaceous accumulations, but 

 especially the " Mullasawnites " and the " book sandstones " of the 

 Manor cunningliam group, counties Tyrone, Donegal, and Londonderry, 

 make in very similar masses to the quartz- rocks of Carrick Mountain, 

 county Wicklow, and those of the Forth Mountain, county Wexford. 

 They, occuning in massive and lenticular protrudes, have false 



' From Griffiths' map it is evident that that eminent geologist observed, in some 

 places, a difference between quartzite and quartz-rock ; but in general he did not 

 separate the one from the other. 



-Vol. viii. New Series, Journal Roy. Geol. Soc., Ireland. 



