280 PROFESSOR T. G. BONNET ON A COLLECTION OF 
above Hanigon, to the west of the former locality,” the felspar is less altered, and 
some of it, if we may trust the optical tests, is albite, and more of the green mineral 
appears to be an altered mica. Among the Archaean rocks on the right bank of the 
upper part of the Gollonsir Valley are two dykes. One of these [4145], a dark 
speckled rock with the felspathic constituent weathering yellow, consists of long 
narrow crystals of rather decomposed plagioclastic felspar and a lrornblendic mineral; 
some of this shows very characteristic cleavage, other crystals when cut parallel with 
the edges of the prism exhibit a rather fibrous structure and look as if they might be 
of secondary origin. One or two possibly replace magnesia-mica. There is a little 
quartz, epidote, and some black iron peroxide, with, perhaps, a little apatite. The 
other dyke has much of its hornblende in long narrow crystals with the same secon¬ 
dary aspect, and the felspar crystals also, which to a great extent are replaced by 
secondary microliths, are long and narrow like those of a dolerite. A third specimen 
[4197] from a rock on the bank of a stream is of the same character, but rather more 
porphyritic. Many of the felspar crystals show a zonal structure, and the outer part 
remains clear, while the inner is replaced by secondary microliths. The small extinc¬ 
tion angle, where observable, leads me to conclude that oligoclase is the dominant 
felspar. In this slide magnesia-mica is recognisable. 
From the tracts traversed on the east of Ghubbet Kurmeh a remarkable rock has 
been brought, which, with some hesitation, I class among the diorites. The compact 
matrix is a dark blue, almost black colour, in which are thin crystals of felspar often 
nearly 1" long. With the microscope the ground mass is seen to consist of small 
elongated felspar crystals having a rather fibrous or “ teazed ” aspect, associated with 
much opacite and some green microliths of hornblende or chlorite, rather irregularly 
disseminated, and some flakes of brown mica. The larger crystals of plagioclase 
felspar show the greatest absorption at very small angles with the vibration planes of 
the crossed nicols, and parallel lame!he extinguish almost simultaneously, so that they 
are probably oligoclase. The hornblende, however, has very much the aspect of a 
secondary product, and I am disposed to regard the rock rather as a lrornblendic 
diabase than a true diorite. 
From an isolated hill in the middle of the Gharrieh Plain (mainly limestone), which 
is covered with a peculiar vegetation, come some dioritic rocks (associated apparently 
with granites or granitoid gneisses). One of these consists of a plagioclastic felspar, 
which (though in part replaced by microliths) from its large angle, where unaltered, 
between successive extinctions (often quite 30°) is probably, in part at least, anorthite, 
and of hornblende, also with a secondary aspect, some chlorite, with epidote, apatite, 
and a dichroic fibrous lamellar green mineral, which extinguishes parallel with the 
lamellae, and is more probably an altered mica than hornblende. A few grains of 
quartz are also present. 
Other lrornblendic rocks were noted during my examination of the specimens. 
Those described above certainly appear to be in all cases igneous rock, but it is quite 
