PROFESSOR HEDDLE ON THE MINERALOGY OF SCOTLAND. 219 
of the granular quartz and flakey mica,—incorporating them in its mass,—the 
magma, upon resolidification, would assume the form of a granitic breccia, or a 
granite, according to whether the felspar, in its action as a solvent, failed or 
succeeded in accomplishing the solution of the other two minerals. 
A friend, however, of far greater petrological experience than myself, and 
much more extended knowledge of the district in which they occur,—one, 
moreover, to whose opinion I pay so much deference, that I am almost afraid to 
differ from him, holds these layers to be granitic veins. I have indeed been shown 
localities where hand specimens of these layers could not be called anything 
but granite ; but where, in my opinion, the rock as a whole was as unmistakably 
gneiss. These localities are however, I believe, all in the neighbourhood of 
the granite ; and, though it may not be possible to show it everywhere, there 
are localities where,—the metamorphism affecting the rock as a whole,—the 
gneissose structure may be seen gradually to fade away into the gray granite 
of Aberdeenshire; so that no two authorities would agree where the one rock 
ceases and the other commences. 
And if the nature of the rock here is puzzling, so are the specimens of the 
felspar difficult to recognise. 
The first specimen analysed was handed to me by Professor Nicot as oligo- 
clase, from Banchory ; and this it was considered by myself also to be, till the 
cleavage angle was measured. I obtained specimens of it myself, about a mile 
north of Blirydrine, in Kincardineshire, where it is associated with pale 
green apatite and brown Haughtonite, which here weathers green. The ortho- 
clase itself in this district is so largely graphically charged with quartz, that 
it is but seldom that specimens can be sufficiently separated from it for. 
analysis. Throughout the whole of Deeside, especially in localities adjacent to 
limestone, the felspar is of the same type. 
Colour, that of skim milk ; weathers buff; lustre, somewhat fatty ; cleavage, 
89° 41’; specific gravity, 2° 551. 
25 grains gave—- 
Silica, . ; ; ; ; sel Gow 59 
Alumina, : : : ; Seer Git 5 S82 
Ferric Oxide, As) See ate HOSS 
Lime, . ; : 3 : : * 682 
Magnesia, : : . . 08 
Potash, : ; : : Sieh a5) 
Soda, . . : ; ‘ : 2°76 
Water, . : 3 P 5 ; 491 
100: 733 
Possible impurity, quartz. 
