238 PROFESSOR HEDDLE ON THE MINERALOGY OF SCOTLAND. 
There is at least no mistaking his “beautiful rock,” so well does it deserve 
the name ; even in hand specimens nothing can be more striking than the con- 
trast presented by the succession, in varying thicknesses, of the different‘layers 
of its two mineral constituents. But I am unable to agree with him as to their 
nature, as I am unable to admit that the beds of quartz mentioned should be 
called quartz. 
The beautiful rock les immediately to the west of the dark serpentine, 
near the south-west corner of the Voe. After a hasty examination it would be 
pronounced hornblendic gneiss ; closer inspection inclines one to believe the 
green mineral to be more probably augite than hornblende, while the white 
layers should hardly have been taken for a granular quartz. The use of the 
knife would have determined the absence of any quantity of quartz. 
; It is a portion of the largest and purest band of the white mineral of which 
the analysis is now given. Structure,—a granular mass of crystals lying in every 
direction—the crystals are not striated ; (the augite (funkite) crystals are all 
platey, or parallel to the bands of the felspar.) 
Colour, white ; specific gravity, 2 622. 
1°544 grammes gave— 

Silica, . : . 66°80 
Alumina, . 2 oT 832 
Ferrous Oxide, .  Seest28 
Magnesia, .. . ‘ *138 
Lime, : y . 1:°504 
Potash, : : ‘ -919 
Soda, . : A oe Lae ony 
Water, : : "484 
100 - 322 
Of the silica 1-591 per cent. were insoluble ; possible impurity, quartz and 
funkite. 
4. Hippert’s so-called “ quartz vein” proved, on examination, to be a bed of 
a splendent white felspar, plentifully interspersed with quartz graphically ar- 
ranged. The bed lies on the other or east side of the serpentine, and closely 
adjacent to a bed of dense granular white limestone. This is the finest 
massive albite in Scotland; though there are no free crystals, its cleavage 
faces are of large size, great purity of appearance, and brilliancy of lustre. 
It very rarely exhibits striation. It is separated from quartz with great 
difficulty. 
Its cleavage angle is 86° 45’; its specific gravity 2° 61. 


