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PROFESSOR HEDDLE ON THE MINERALOGY OF SCOTLAND. 215 
From exjiltration Veins in Granite. 
7. From the great vein in Rubislaw quarry, near Aberdeen. This vein 
being now quite covered, and my attention not being directed to the subject 
when I last saw it uncovered—now many years ago—I cannot affirm that it is 
an exfiltration vein ; it certainly was not like those of that class at present to 
be seen in the quarry. 
Twins of orthoclase of large dimensions are now and again to be seen at 
Rubislaw ; several years ago I measured one eight and a half inches in length, 
from the above vein; and in the summer of 1876 one was measured by 
* Professor Nicot and myself which was eight inches in width. 
These crystals are lustrous on their cleavage faces, of a reddish flesh colour, 
and in parts translucent. They exhibit at times the peculiarity of structure 
already mentioned, which here at first sight somewhat resembles the striation 
of repeated twinning. 
In addition to these giant crystals of felspar, the old vein of Rubislaw 
afforded as associated minerals, fine specimens of tourmaline, garnet, beryll 
(Davidsonite), apatite, and muscovite,—all imbedded in a paste of quartz. 
There are also present large crystals of a black, slightly biaxial mica, which 
differs from lepidomelane in having almost all the iron present in the state of 
protoxide,—as in the magnesian Biotite. The description and analysis of this 
new mica will be afterwards submitted, under the name of Haughtonite. 
A pure fragment of the orthoclase, obtamed and analysed in 1856, with 
cleavage angle 89° 58’, and 8. G. 2°554, gave— 
Silica, 3 vi 3 ; 64°54 
Alumina, . ; ; . 18-36 
Ferric Oxide, . é 4 “32 
Magnesia, . : : : “09 
Lime, : ; : : *36 
Potash, ; P A pate o)i51 015) 
Soda, : Z : oe OO 
Water, : : : 3 * 086 
99 - 386 
1:33 per cent. of the silica insoluble. Possible impurity, quartz or muscovite. 
From eajiltration: Veins in “ Syenitic Granite.” 
8. From a vein in the wood on Cnoc dubh, about a mile east of Lairg, 
Sutherland. 
This granite consists of little quartz, much white felspar (? oligoclase), much 
hexagonal black mica (Biotite ?lepidomelane), no muscovite, rarely sphene, 
and very rarely any hornblende. The propriety of the term syenitic is therefore 
very questionable. 
