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PROFESSOR HEDDLE ON THE MINERALOGY OF SCOTLAND. 493 
may defy individual recognition, from the similitude of kaolin to serpentine 
itself. Such an intermixture may account for the large quantity of alumina in 
some serpentinous rocks; indeed, any serpentine rock which contains much 
alumina may be held to have originated from a primary rock of which one or 
other of the felspars was an ingredient. 
Change by Hydration ; removal of Lime; of Silica; and partial peroxidation 
of the Iron. 
Pseudo-Augite. 
21. Portions of the larger bed of serpentine to the west of Portsoy form, when 
polished, a highly ornamental stone, there being a mixture of blotches of a bright- 
red colour throughout a groundwork of green and white. These red blotches 
here and again assume regular forms—-those namely of augite ; they are simply 
pseudomorphs thereof, set in a matrix composed of green steatite, a pale-green 
hydrated asbestus, and ordinary serpentine. The rough crystalline forms are 
one or two inches in length; they are sometimes isolated, sometimes radiate 
from each other, or form a layer of a basement-like structure. 
They are seamed with a reticulation of a somewhat darker and slightly 
harder substance ; but are otherwise homogeneous, and of a minutely granular 
structure. 
On 1°302 grammes— 
Silica, ; : ‘475 
From Alumina, . (nla 
- 486 = Su ea eal 
Alumina, . : Seo tess 
Ferric Oxide, . : gD 42357 
Ferrous Oxide, . eee 047 
Manganous Oxide, . : 384 
Lime, ; : : pee lee 
Magnesia, ; : oo) pla 
Potash, |. . : ; * 875 
Soda, ; : < : aoe 
Water, . ; ; 5 seeye! 
100: 144 
Insoluble silica, 1 - 646 per cent. 
As regards the proportions of silica, alumina, and water, this is a true ser- 
pentine ; the abstraction of iron is, however, only partial, and the peroxidation 
of part thereof gives the red colour. 
22. An increase in the extent of the peroxidation is seen in the following 
case :— 
VOL. XXVIII. PART IL. 6M 
