244 PROFESSOR HEDDLE ON THE MINERALOGY OF SCOTLAND. 







6. From Rubislaw Quarry. No better illustration of exfiltration veins could 
be seen than those from which the fine oligoclase now noticed was taken. 
Two great tortuous tears are to be seen in the depth of the quarry crossing the 
jointings more than once, but fading away at both ends into the unruptured 
rock. These tears are filled up with a mass of crystals of grey-pink orthoclase, 
milk-white oligoclase in large twinned crystals, crystallised muscovite, Haugh- 
tonite, apatite, schorl, and rarely garnet, in a paste of quartz. 
At the centre of the wider portions of the rents these crystals are of consider- 
able size ; but that diminishes towards the sides until they graduate down by 
insensible transition to the dimensions of the crystals of the rock itself. There 
is no line of demarcation, no slickenside markings, and no interstitial mineral, 
or skin,—as in the case of intrusion veins. 
The crystals of oligoclase are so minutely striated as to require the aid of a 
powerful lens, for the detection of the lines. 
Their cleavage angle is 86° 14’; their specific gravity, 2° 637. 
1°476 grammes yielded— 
Silica, : : . °909 
From Alumina, . . *014 
923 = 62 533 
Alumina, . ; : » Bo ols 
Ferric Oxide, : : VDOT 
Magnesia, . é : ; 365 
Lime, . : ! : EST 
Potash, x : : .) epee 
Soda, . : ; % a ab eee 
Water, . : : : ; “6 

100°777 
Insoluble silica, 2° 845; possible impurity, orthoclase or quartz. 
7. From the Quarry of Cragie Buckler, near Aberdeen. The specimen was — | 
sent me by Professor Nicot. 
It was very similar in appearance to that described from Sclattey; the a 
associated minerals were the same ; the only difference being that the imbedded . 
urystals of oligoclase were better defined, larger, more distinctly striated, and — 
the striz much coarser than those from the former locality. } 
Cleavage angle, 86° 14’; specific gravity, 2° 622 
