PROFESSOR HEDDLE ON THE MINERALOGY OF SCOTLAND. 543 
somewhat granular crystals, apparently of augite, of the size of large shot, 
which are imbedded, singly or separately, in a waxy-looking massive labradorite. 
In this rock a vein of a pale sap-green mineral was found by Professor 
Nicox and myself. This was set down by my friend as precious serpentine ; to 
me it appeared somewhat too hard for this, as it cut with less ease than slate- 
pencil. It was translucent, tough, and had a specific gravity of 2 - 59. 
On analysis it afforded— 

Silica, : . : . ene tol 
Alumina, . , : . 12°444 
Ferrous Oxide, . é . 2°684 
Manganous Oxide, . Sept Liea! 7 
Lime, : ; : oh MOS 
Magnesia, . : ‘ . 34°098 
Water, ‘ 4 F 5 Lord 
99 +822 
Now this is precisely the composition of the massive variety of penninite which, 
from its resemblance to serpentine, has received the name of pseudophite. 
But it may also be regarded as a highly aluminous serpentine ; for if that earth 
be abstracted the residue is just serpentine. The point of interest which 
attaches to this substance is, that although it formed a true exfiltration vein in 
the rock, if the rock in contact with the vein be examined, the waxy labradorite 
is also seen to pass, within a space of about an inch, into this mineral by insen- 
sible gradation. So it matters not whether it, in a systematic arrangement, be 
consistently classed with penninite or not, it is here unquestionably a transmu- 
tation product, the result of a serpentinows change of the labradorite. 
The modus operandi of the change of felspar into serpentine is much more 
subtle than that of the conversion of augite, and also, it must be said, much 
less certain. As labradorite contains much alumina, and no magnesia, we 
have, in z7és serpentinous change, to account for the removal of alumina and 
the direct insertion of magnesia. The term “ magnesian process” may with 
perfect fitness be applied to such a change. 
Such an action as that above shown to suffice for the transmutation of 
augites could not in any degree effect a similar change in labradorite; car- 
bonated waters do not affect silicate of alumina, and carbonated waters cannot 
directly purvey magnesia. 
It is true that immediately over the bed of serpentine at Portsoy which 
evidenced such a change, there is a washed out bed of something, and it might 
be argued that that something had been dolomitic limestone; which would 
yield bicarbonate of magnesia to waters passing through it ;—which bicar- 
bonate of magnesia, by a recognised interchange with silicate of lime, would 
yield silicate of magnesia. To such a view it has to be replied, first, that there 
