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14. THE GEOLOGY OF AUCKLAND

have been informed by Mr Heaphy that these rocks are of
wide-spread extent in the Middle Island, forming mountain
ranges of great altitude, covered with perpetual snow, and
reaching in Mount Cook probably to 13,000 feet. The rocks
of these formations contain the principal metallic riches of the
earth. Therefore we cannot hope to find these riches developed
in the highest degree in the Northern Island; but as other
formations also contain metalliferous veins, there may be found
many mines worth working in the rocks I am about to describe.

I. - PRIMARY FORMATIONS.
The oldest rock I have met with in the Province of Auck-
land belongs to the primary formation. It is of very variable
character - sometimes being more argillaceous, of a dark blue
colour (when decomposed, yellowish brown, the colour generally
presented on the surface,) and more or less distinctly stratified
like clay slate - (at Maraitai on the Waitemata); at other times
the siliceous element preponderates, and, from the admixture of
oxide of iron, the rock has a red, jasper-like appearance - (at
Waiheki, Manganese Point.) In other localities it is more dis-
tinctly arenaceous, resembling the Old Sandstones of the Silurian
and Devonian Systems, called Grauwacke - (at Taupo, on the
Hauraki Gulf.)

As no fossils have yet been found in this formation in New
Zealand, it is impossible to state the exact age; I am, however,
of opinion that these argillaceous siliceous rocks will be found to
correspond to the oldest Silurian strata of Europe.

The existence and great extent of this formation are of con-
siderable importance to this Province, as all the metalliferous
veins hitherto discovered, or likely to be hereafter found, occur
in rocks of this formation.

To these rocks belong the Copper-pyrites, which has been
worked for some years at the Kawau and Great Barrier - the
Manganese (Psilomelan) at Waiheki - and the Gold-bearing
quartz at Coromandel.

The gold which is washed out from beds of quartz-gravel in
the rivers and creeks flowing down from both sides of Coro-
mandel range, is derived from quartz veins, of crystalline char-
acter and considerable thickness, running, in a general direction