
PROFESSOR HEDDLE ON THE MINERALOGY OF SCOTLAND. 265 
felspars, there are rocks in which orthoclase finds no place :—its lithological 
habitudes are therefore clearly defined. 
Albite in Scotland is confined to the somewhat hornblendic and epidotic red 
granite of Peterhead, the rare associates being agalmatolite and fluor.* 
A rock sui generis, which is associated with serpentine, and which stretches 
m a belt from Fetheland Point to Hillswick Ness, contains it in association 
with hornblende or with augite ; a graphic vein near serpentine, at Bigsetter 
Voe, may be an offset from the above. 
An exceptional occurrence is that of the moonstone of Stromay, where it 
would appear to replace oligoclase. The lithological relationships of albite in 
Scotland are therefore ill-developed, if not also ill-defined. 
Anorthite in Scotland seems to replace oligioclase in the diorite of Fetlar, 
and in portions of the gabbro of Ayrshire ; as Latrobite it very rarely is found in 
granular limestone in Glen Gairn. Its relationships therefore are also ill- 
defined. 
The habitudes of the other—the doubted—species are much more definite 
and clear. 
Labradorite finds its place, admitting no other felspar to play its part, or 
even associate itself with it, in all the varieties of diabase,—gabbros, primitive 
greenstones, diallage rock, “ heathens” —or whatever name their varying features 
may procure them—from Balta to Ballantrae. Showing a slight tendency to 
pass over to anorthite very rarely; only in one case (Fetlar) yielding to it. 
Even when in Glen Bucket the rock actually passes into diorite, the felspar is 
unchanged. 
Nor has it stepped far afield when it also asserts itself as the felspar special 
to the porphyritic amygdaloids of the south-west and north-east. Le Hunr 
showed it to be the felspar of the traps on both sides of the Clyde; and we 
now find it to be that of Bervie, Kinneff, Thornyhythe, Tremuda, and all that 
coast. 
Nothing could be stronger than the evidence of the rocks as to the specific 
individuality of this mineral. 
Oligoclase again presents itself as the very frequent associate of the corded 
felspar in granitic veins t—-only in one locality (Coyle) is it found in another 
association ; the evidence as regards it is also perfectly definite. No one who 
has become familiar with the ever-recurring exfiltration veins—called crocus by 
the quarrymen—which lace the grey granite of Aberdeenshire, will hesitate in 
* The “felspar” of the rock of Corstorphine Hill is usually called albite,—it has not been 
analysed. 
+ It also constitutes the bulk of the grey granite of Aberdeen; this I find to consist of a great 
deal of oligoclase, little orthoclase, little quartz, very small quantities of muscovite, and a good deal of 
,Haughtonite, such a compound as G. Rose calls granitite. The hornblendic gneiss of the Cape 
Wrath district frequently consists almost solely of a granular mixture of oligoclase and hornblende. 
VOL. XXVIII. PART I. oz 
