Page:Transactions NZ Institute Volume 15.djvu/490
In 1868 a specimen, also consisting chiefly of sulphate of alumina, was forwarded for identification by Mr. G. Richardson from Rancowers Island, Manawatu.
Alum, Ṙ + (, ) 3 + 24 Ḣ.—The first mention of the occurrence of this mineral in New Zealand is by Dr. v. Hochstetter (New Zealand, 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 | 11.80 |
| Sulphate„ of„ protoxide of iron | 5.27 |
| Sulphate„ of„ sesquioxide of iron | traces |
| Sulphate„ of„ lime | 1.31 |
| Sulphate„ of„ soda and potash | 14.60 |
| Chlorides | traces |
| Insoluble in water | 33.30 |
| Water and loss | 33.72 |
| 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—
| Alumina | 10.40 |
| Ferric oxide | 1.11 |
| Lime | .50 |
| Magnesia | 5.46 |
| Soda | .41 |
| Sulphuric acid | 37.40 |
| Hydrochloric acid | traces |
| Water | 42.72 |
| Insoluble in water | 2.00 |
| 100.00 |