KiXAHAX— 0>2 Granitic and other Ingenite Rocks. 131 



patches of a green mineral, called by the miners j?(?ff(?7; /'* also with 

 drusy cavities, or small vugs, Kned "with crystals of quartz. 



The rocks in the veins may vary. In some places, so siliceous as 

 to look like quartzyte, and in a few it is a finely crystalline white 

 rock, in which the quartz and mica are so minute that they can scarcely 

 be detected by the naked eye. In a dyke on Shannaunnafeola, the 

 centre is a fijaely crystalline aggregate of quartz, orthoclase and 

 black mica, while the outside portions near the walls are coarsely 

 crystalline compound of qiiaitz, orthoclase, white mica, and pyrite, the 

 latter constituent being conspicuously abundant. This vein was in a 

 neighboiu-liood where there are granites that are evidently metamor- 

 phosed felstones, and possibly it may also belong to that class. In a 

 few veins, part of the mica, white probably muscovite, has a plumose 

 arrangement, as if pkunes of feathers were pasted down on surfaces of 

 the rock. The surfaces in those places where this arrangement was 

 noted were parallel, or nearly so, to the walls of the veins. This 

 variety appears to be similar to the rock described by Jukes, and called 

 plumose-granite. 



jS^orth-east of Eecess, in the townland of Derrynea, there is a vein, 

 having in the centre a coarsely crystalline rock, while towards the 

 walls the rock is of a fine textiu-e. In the hill called Lisoughter, and 

 also in other places in the barony of Ballynahinch, peculiar veins were 

 observed, being very coarsely crystalline, the quartz and the felspar 

 occurring in masses often the size of a man's fist, while the mica is 

 proportionally large. In these rocks usually the mica is of a silvery 

 palish olive-green or a whitish colour, but black mica may also occur 

 in small flakes. The large mica is sometimes most peculiarly arranged, 

 so that on weathered sui'faces the edges of the flakes have angular 

 forms, as if the rock was inscribed with some kinds of vrritten charac- 

 ters. In other veins, that appear allied to those last described, and 

 always when they traverse or are in juxtaposition with limestone, 

 patches may lose all their mica, while the quartz and felspar are arranged 

 like Hebrew characters, answering the description of the rock that has 

 been called grapMc granite.] The granite veins last described are evi- 

 dently different to the first, and seem to be newer than them. Possibly 

 they may belong to the class called endogenous by Hunt, while the 

 others belong to his exotic rochs.\ 



The gi'anite in mass may also have varieties. In some places it 



* The true blue peach of the miner is ripidolite, and the mineral in these nests 

 is very like it in aspect and feel, but it has not been analysed. 



t Hunt mentioned veins of gi-aphic granite associated with limestone among the 

 American rocks. [American Journal of Science and Arts, Thii'd Series, vol. i., 

 No. 3, p. 183). 



X These veins I believe not to be tnte granite dykes, but rather to belong to the 

 class called " granitic-veinstone" by Hunt. I, hoM-ever, here describe them, as 

 other authorities class them -n-ith the true granites. The vein rock just desciibcd 

 in Derrvnea mav also belong to Hunt's " endogenous rocks." — Eeport Geol. Survey, 

 Canada," 1865, p". 192. 



