* 
288 PROFESSOR T. G. BONNEY ON A COLLECTION OF 
northern side of the Haggier Mountains, inland from Hadibu. The gully is excavated 
in the coarse reddish pegmatite, which is cut by a vein granite [4264] (p. 282). This 
mica-trap is a rather compact variety consisting of a reddish felspar, mica, and a dull 
greenish mineral. Microscopically it consists of felspar, mainly orthoclase, in which 
are scattered numerous microliths of opacite, hornblende and mica, with larger crystals 
of brown and white mica, chiefly the former, hematite and hornblende, the last being 
often crowded with opacite and clear microliths, perhaps apatite. The rock then is a 
minette and follows its usual habit of occurring in a dyke or vein. 
From the shore west of Hadibu, near the argillites (p. 289), comes a very minutely 
crystalline rock of dull-grey colour, which when microscopically examined consists of 
decomposed felspar, probably plagioclase, altered magnesia-mica, iron peroxide, a 
little hornblende, apatite (?), and interstitial quartz. This then is a kersantite. 
From between Kami and the hamlet Ma-aber, on the Motaha, comes a minutely 
crystalline rock [4309] associated with felspathic granitoid rocks already mentioned 
(p. 276), which consists of pale grey felspar, mica, and some quartz, grains of each 
occurring porphyritically in the ground mass. The microscope shows that a good deal 
of the felspar is plagioclase, some being oligoclase, but orthoclase is also present; the 
larger crystals often enclose numerous clear microliths, there is also much biotite and 
some quartz, with grains of iron peroxide. The rock then is a quartz-kersantite. 
Unaltered clastic rocks. 
Passing now to the comparatively unaltered clastic rocks, we have first to notice the 
agglomerates or conglomerates from the district near Kittim, where they occur in large 
masses in association with the rhyolites as already described (p. 277). .There are 
conglomerates and breccias (generally rather decomposed) of a compact red rhyolitic 
rock, some of which reminded' me in appearance of the specimens of late Precambrian 
age, which are so common to the west-south-west of Bangor, a mile or two from the 
town.* 
[4437] has been examined microscopically. It is composed of fragments of rhyolitic 
lava, subangular to rather rounded, with some quartz grains, containing very minute 
cavities, and a very little of a cementing matrix, which is generally stained with ferrite 
or viridite. The lava fragments vary considerably in their structures. One, containing 
some small felspar microlites, has a marked fluidal structure, being banded with very 
dark ferrite; it is almost certainly a fragment of scoria or from the slaggy exterior of 
a lava flow; others exhibit various fluidal and microlithic structures. Most of them 
are ferrite stained, and more or less devitrified : materials derived probably from more 
than one source. There are also some grains of viridite, these being probably altered 
fragments of augite or hornblende. The rock is a rhyolitic grit, the materials of which 
are certainly of volcanic origin, but probably (in this particular case) have been 
transported by water. The resemblance already noticed to the Welsh Precambrian 
* Quart. Journ. Geol. Soc., vol. xxxv., p. 309, and Geol. Mag., Dec. ii., vol. vii, p. 298. 
