164
THE NEW ZEALAND GAZETTE.

uppermost." And the organic remains are, as many mines worth working, in the rocks I am
Dr. Mantell beautifully expresses it, the "coins about to describe.
of Creation," which give us the means of trac-
ing the history of the development of the
organic kingdoms.

Thus, by superposition and by their organic
remains, the aqueous rocks are divided into
groups forming, in reference to their age, what
is termed an " ascending series," or beginning
with the oldest, in the following manner:—

1. Primary formations or periods.
2. Secondary
3. Tertiary
4. Quartary
   دو
   "
   "
   "

In reference to the word "quartary" I may
explain that, although it is not an English
word, I take the liberty to use it in the sense
of "post tertiary," as following the analogy of
the other terms.

Each of those formations is again divided
into numerous minor systems, on which I have
no time to enter.

The fourth and last great division of rocks
are the volcanic-as Trachyte, Basalt, Breccia,
and Tuff-all produced by supramarine or sub-
marine volcanic eruption. It is ascertained
that the earliest true volcanic eruptions have
occurred subsequently to the Secondary period,
commencing in the Tertiary, and continuing to
the present time; and it is a marked difference
between the older and the more recent
eruptions.

I have prepared a diagram which will serve
to impress these first principles upon your
memory, and so enable you to follow me in
the account I have to give :—

DIAGRAM.
Origin.
Plutonic and
Metamorphic rocks
Aqueous
Volcanic..
Age.
Primitive
formation.
Primary.
Secondary.
Tertiary.
Quartary.
Trachytic.
Basaltic.
Organic Remains.
no fossils.
} Fossiliferous.
no fossils.

With these preliminary remarks, I now
proceed to the main subject of my lecture.

GEOLOGY OF THE PROVINCE OF AUCKLAND.

The first striking characteristic of the
Geology of this Province-and probably of
the whole of the Northern Island of New
Zealand-is the absence of the primitive,
plutonic, and metamorphic formations, as
granite, gneiss, mica-slate, and the like. I
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
I.—PRIMARY FORMATION.

The oldest rock I have met with in the
Province of Auckland 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 strati-
fied like clay-slate-(at Maraitai on the Wai-
temata); 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 distinctly arena-
ceous, resembling the Old Sandstones of the
Silurian and Devonian Systems, called Grau-
wacke (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 considerable 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-bear-
ing quartz at Coromandel.

The gold which is washed out from beds
of quartz-gravel in the rivers and creeks flow-
ing down from both sides of Coromandel
range, is derived from quartz veins, of crys-
talline character and considerable thickness, run-
ning, in a general direction from North to South,
through the old primary rocks which form the
foundation of the Coromandel range. In
some places these veins stand up like a wall on
the summit of the range to a height of eight
or ten feet. The clay-slate rock itself is
exposed only at the bottom of deep gorges which
form the channels of the principal streams.
In almost all places it is covered by large
masses of trachytic tuff and breccia, of which the
hills surrounding the Harbour of Coromandel
are composed. The well-known "Castle
Hill"-which can be seen from Auckland-is
a characteristic example of the Trachytic Breccia
formation. The magnetic iron-sand which, in
washing, is found with the gold, is derived
from the same source as all the magnetic iron-
sand of New Zealand, namely, from the de-
composition of trachytic rocks. Small veins
of quartz of amorphous character-that is, not
crystalline, but in the shape of chalcedony, cor-
nelian, agate, and jasper-are found in numerous
places on the shores of Coromandel. These
veins occurring in trachytic rocks, are quite
different from the auriferous quartz veins in
the primary formation, a fact, I think, of
much practical importance to state, to prevent