III.—CHEMISTRY. 
Art. XLVIIIL.—On the Pottery Clays of the Auckland District. 
By J. A. Pon. 
[Read before the Auckland Institute, 20th August, 1883.] 
In the year 1876, I had the honour of reading a paper before this Institute 
on “a few of the fire-clays of this district,” since which period the frequent 
opportunities I have had of examining the different deposits has led me in 
no way to alter my opinion as to the great value and extent of them, and 
since then I have seen and examined so many other beds of these alluviums 
that I make no apology for bringing before you to-night a few notes upon 
another series embraced in the very extended term, pottery clay. By this 
is meant that material of which the finest of our china and parian ware, 
and the roughest of our earthenware, are made; from the pure white kaolin 
obtained by the disintegration of the granite, to the rough ochreous clays 
and marls whose red and grey tints are so well known. Included with these 
is the terra cotta, a soft unctuous clay with a large percentage of peroxide 
or carbonate of iron regularly distributed. This, if of good texture and 
thoroughly admixed, will yield in the muffle a biscuit of the most delicate 
shades of redness ; this is terra cotta, the use of which has increased very 
much of late in England, large houses being built entirely of it. 
In dealing with the commercial values of heavy materials, such as clay, 
full consideration must be given to the removal of the same for shipping 
purposes, the carriage to market being always a serious factor. In dealing 
with this subject I have not been unmindful of this factor, and clays which 
are really of value on account of their texture or purity are passed over on 
account of the impracticability of bringing them to market. 
Of the clays I have examined the great majority lack the whiteness of 
the true kaolin, and the biscuits from them vary from white to a full bright 
red. Those having light creamy tints to buffs are very plentiful, and I have 
no doubt that in many of these instances, when the beds are properly opened 
and worked, they will improve in uniformity and whiteness. 
From Mongonui and Awanui I have received samples of excellent 
pottery clay, some being nearly white, but the majority of a cream tint. 
From Whangaroa I received through Mr. Will a sample of pipe-clay of pure 
whiteness, very unctuous and refractory, a nearly pure silicate of alumina, 
There is, I believe, a large deposit of this material. From the Bay of 
Islands I have obtained clays of fine texture, fairly white, perfectly free 
