The Quarterly journal of the Geological Society of London (13365530803)

1850.. DAWSON METAMORPHIC ROCKS OF NOVA SCOTIA. 361

the ochrey red ore. The irregularity of its distribution would result

from that of the carbonate of iron, which, where it now occurs in

the vein, is seen to be confusedly mixed with the ankerite. It might

also happen that the heat would act most powerfully along lines of

fissure, and of this there are some evidences in the appearance of the

vein. The comparatively unaltered state of the ankerite is explained

by the fact, that it is less easily decomposed by heat than the pure

carbonate of iron, or even than the spathose iron found at Acadia

Mine. If a small fragment of the mixed white ankerite and spathose

iron from Acadia Mine be exposed to a low red heat with access of air,

the carbonate of iron is completely decomposed, before any other

change than a slight discoloration is produced in the ankerite.

Hand specimens from the Acadia Mine often present appearances

highly illustrative of the relations of the red ore to the other ingre-

dients of the vein, and confirmatory of the above views of its origin.

Fig. 4 is a sketch of one surface of a specimen of this kind.

Fig. 4. — Surface of a Hand-Specimen from Acadia Mine.

a. Ankerite.

b. Spathose iron.

c. Red iron ore.

d. Fragment of slate.

e. Ankerite with surface changed into yellow ochre.

/. Fissure lined with red ore.

The brown hcematite is apparently confined to the superficial parts

of the vein; and indeed appears to have been more abundant in

those parts of it which have been removed by denudation, than in

any now remaining. It is no doubt a product of the action of water

on the carbonate and hydrated oxide of iron, near the outcrop of

the vein.

The sulphate of barytes, occurring in small quantities in some

parts of the vein, must also be a product of aqueous infiltration.

The facts which I have obtained in relation to the age of this de-

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1850

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