| 
| 
PROFESSOR HEDDLE ON THE MINERALOGY OF SCOTLAND. 513 
The large quantity of water led to the suspicion of alteration, but the powdered 
mineral showed no effervescence with acid. The quantity of alkalies, in presence 
of the fact that a lime felspar is the associate, is also singular. 
14, From the diorite of Portsoy. 
The rock from which the mineral under consideration was taken has, through 
error on my part as to the nature of the hornblendic mineral, been called in my 
paper on the Felspars, diabase. The subjoined analysis of the mineral, taken in 
conjunction with the determination of its cleavage angle, and with the ascertain- 
ing that it is dichroic, shows it to be hornblende, and the rock hence dzorite. 
This diorite first shows itself a little to the west of the Battery; it is here of 
a coarser grain than elsewhere to the east, being formed of labradorite and of 
the mineral in question, porphyritically arranged ; the crystalline masses are of 
an inch in size. 
Of the associated labradorite, the analysis has already been given at page 
256 of these ‘‘ Transactions.” These minerals form the great mass of the rock, 
which here also contains in small quantity, menaccanite, sphene, a dark brown 
mica, and specks of pyrrhotite. 
The hornblende in mass appears dark grey in calene: when closely viewed 
by transmitted light—for it is transparent in small fragments—it is reddish- 
purple, being very similar to some garnets. 
Its cleavage angle is 124° 33’; its specific gravity, 3° 252; it also affords 
the rectangular cleavage. 
1-402 grammes afforded— 
« Silica, . : : - 688 
From Alumina, . * 042 
aie = 52:068 
Alumina, . . : 2 2 50S 
Ferrous Oxide, . é ee QRZ 
Manganous Oxide, . 5 tr. 
Lime, ; : . ae ko O52 
Magnesia, ; ; . 14:°407 
% Potash, . ae ake: : 746 
Soda, ; ; ; ; = 569 
Water, . : : : *852 

99-987. 
Possible impurity, labradorite. 
The determination of the nature of this rock, I regard as one of considerable 
importance, as it will be found to have a very immediate bearing upon the 
| question whether rocks of this class are, as regarded by Corra, wholly or solely 
| igneous,—or, as regarded by Dana, metamorphic. 
VOL. XXVIII. PART II. 6R 
