PROFESSOR HEDDLE ON THE MINERALOGY OF SCOTLAND. 213 
25 grains yielded— 

Silica, ; ; . 64° 745 
Alumina, . ; a WSs 
Ferric Oxide, . ‘ 1:99 
Magnesia, . d ; * 038 
Lime, ‘ ; ; 193 
Potash, : 5 : 983 
Soda, ‘ : d oi050 
Water, : ; : oF) 
Fluorine, . : if tr. 
99-43 
Insoluble silica, 1° 842 per cent. Possible impurity, none. 
5. The fourth vein consists almost solely of felspar; a few imbedded 
garnets, and an occasional imbedded crystal of a bright red felspar (?) being alone 
visibly associated with it. 
The felspar is of very pure appearance, of pale flesh colour and watery 
lustre. S. G.,2°559. Cleavage angle, 89° 40’. 
25°57 grains yielded— 

Silica, . ; : elon Gye 
From Alumina, ; 307 
lé6o Sine (6008 
Alumina, ; 4 tediSaa02 
Ferric Oxide, . , =. 2 4035 
Lime, : : ; ; - 997 
Potash, . : : . 10 0LS 
Soda, . ¢ : fo) coed Ok 
Water, . : : : °165 

100-713 
18 62 per cent. of the silica insoluble; possible impurity, the bright red felspar. 
This analysis of perhaps the purest orthoclase I have examined, so far as 
mere appearance goes, departs more from the formulaic requirements, as 
regards the amount of silica and soda, than any other. An admixture with 
quartz would have partly explained this departure, but there was present no 
visible quartz. It may be microline. 
I cannot even conjecture what the imbedded bright red crystals were— 
they had apparently the lustrous cleavages of a felspar. 
Excepting this difference of one and a quarter per cent. in the silica, these 
two felspars are of nearly identical composition ; the one vein carried little else 
than felspathic matter ; the felspar of the other crystallised out of a melange of 
the constituents of tourmaline, apatite, and mica; or to put itmore correctly, as 
VOL, XXVIII, PART I. 3K 
