PROFESSOR HEDDLE ON THE MINERALOGY OF SCOTLAND. 463 
For the most part this diallage consists merely of a fine-grained melange of 
crystals of the mineral itself with minutely granular labradorite ; but it here and 
again gives evidence of pre-existent stratification in bands or belts of coarse- 
grained structure which hold a uniform and parallel course throughout it. 
These are most highly developed and most easily seen among the winding 
cliffs of Balta and Hunie. 
Here the segregation of matter into giant crystals repeatedly produces the 
appearance of pseudo veins ;—the crystalline masses of diallage which stud them 
being occasionally of the size of the palm of the hand; these lie bedded in still 
larger masses of fine granular labradorite. Even in these localities of higher 
crystalline development, no accessory minerals, with the sole exceptions of veins 
of quartz, carrying epidote, are to be found; the rock, throughout its whole 
stretch, being of singularly simple constitution. 
Of the pseudo veins, the two finest appear on the south side of a little “geo” 
in the island of Balta, which, from its lying to the immediate south of a small 
brough, I have named Brough Geo. Of these veins, which are closely adjacent, 
one carries diallage, the other hornblende. 
It is of this diallage that the analysis is given. In colour it is of a some- 
what dull grass-green, the structure is platey, tending to foliated, the lustre is 
not so pseudo-metallic or splendent as is sometimes seen in this variety of 
augite ; the specific gravity is 2° 965. 
1°501 grammes yielded— 
Silica, : : *'742 
From Alumina, . °012 
754 = 50° 233 
Alumina, . . ; e645 
Ferrous Oxide, . F - eo 223 
Lime, : ; : wee 23 
Magnesia, . . : = 282586 
Potash,-: ;. ‘ ‘ vip Too 
Soda, ; 3 : ; * 582 
Water, . : J 5 ALS ETE 
100° 074 
The quantity of water was sometimes as high as 5° 218. 
Insoluble silica, 2-652 per cent.; possible impurity, labradorite. 
11. From the diallage rock of Pinbain, near Lendalfoot, Ayrshire. 
The relationships of this rock have been so clearly made known by Dr JAmEs 
