886 .Transactions.— Geology. 
In 1868 a specimen, also consisting chiefly of sulphate of alumina, was 
forwarded for identification by Mr. G. Richardson from Rancowers Island, 
Manawatu. 
Alum, Å Š + (Al, Ee) Š’ + 24 H.— The first mention of the occur- 
rence of this mineral in New Zealand is by Dr. v. Hochstetter (New Zea- 
land, 1863, Eng. ed., p. 408), who states that on Puai Island, in the 
Rotomahana Lake, he found films of fibrous alum under cakes of siliceous 
deposit. 
Dr. Hector mentions its occurrence as a product of decomposition of 
pyritous shale at Waikouaiti (Jurors’ Rep. N.Z. Ex., 1865, p. 35), and 
(p. 421) he states that aluminous shale is generally associated with the 
brown coal formation. An analysis of some shale that had undergone 
natural decomposition, and was covered with an efflorescence of alum, 
gave— 
Sulphate of alumina.. ar ME E 
= » protoxide of iron = 5°27 
$3 » Sesquioxide of iron — .. traces 
5 , lime ~ 1:31 
hc 3, Podi SEM potash 5.1, 14:00 
hlo: iraces 
inb. in de D 88:8 
Water and loss oe E s. DO PH 
100:00 
the insoluble matter being principally angular fragments of schist. He also 
mentions (Jurors' Rep. N.Z. Ex., 1865, p. 438) the occurrence of potash 
alum in shale at Tokomairiro, and the Auckland Local Committee exhibited 
specimens of alum from Rotomahana. 
In 1866 Mr. T. R. Hacket collected some magnesian alum from D’Urville 
Island, where it is found as delicate acicular crystals, of a pure white colour, 
grouped in large botryoidal masses, the exterior surfaces of which are of a 
yellowish colour from the presence of basic sulphate of iron. It has a sour 
and slightly astringent taste, is very soluble in water and intumesces on the 
application of a gentle heat. In the blowpipe flame after desiccation it is 
infusible ; displays considerable incandescence and yields the reaction of 
soda. Its composition is— 
umina 3 s Ae EUN IE 
Ferric oxide .. E x^ i IH 
ime .. ee "50 
Magnesia 5:46 
Soda .. 5s = 2h 41 
Sulphuric acid ih = is 84:40 
— acid traces 
Wat s 2 s- AES 
Insoluble i in water $a SE ja 2-00 - 
