Bauxite Deposits In Northland Analysed

Press, Volume CI, Issue 29748, 15 February 1962, Page 11

Bauxite Deposits In Northland Analysed

Results of investigations into bauxite (aluminium) deposits at Otoroa in the KaeoKerikeri district of Northland “have supported the initial enthusiasm for this project,” according to the director of the Geological Survey, Department of Scientific and Industrial Research (Mr R. W. Willett). Mr Willett makes the statement in his foreword to a new bulletin on the investigations, issued by the department. The report, written by Messrs D. Kear and B. C. Waterhouse, of the survey, and Dr. L. D. Swindale, director of the Pottery and Ceramics Research Association, says that in areas totalling just over one square mile north-east of the KaeoKerikeri road, the bauxite is at least 10ft thick, and in part of the area at least 15ft thick.

The weight of bauxite in the deposits is assessed about 20 million tons. The probable analysis of the bauxite is 37.4 per cent, aluminium oxide (alumina), 5.5 per cent, silica, 23.3 per cent, ferric oxide, 2.3 per cent, ferrous oxide, 6.4 per cent, titanium oxide, and 23.6 per cent, water. The probable extractable alumina content is just over 30 per cent.

In addition to these deposits, neighbouring areas of 250 acres may also contribute to the total, but more detailed prospecting would be necessary to confirm this, the investigators say. There is a definite indication of increasing richness downwards, so that areas previously rejected on the basis of shallow drilling are worth further investigation. Kerikeri basalt lava flows similar to those in which the Otoroa bauxite is formed occur at Takou, Manginangina, Tahoranui, Te Whau, Te Pene, and Okaihau, all in the same general area. The investigators think

these flows could well repay further research. They believe that the Takou flow is the most likely to be of the same order as the Otoroa deposits, but that an investigation of the whole area could increase the known amounts of suitable material by as much as five times.

Dr. Swindale says that the removal of the bauxite material from the flows should improve the agricultural value of the area by exposing strata of greater natural fertility. By-products of the production of alumina, he says, could be pig-iron and ferro-titanium.

The deposits were discovered by Dr. Swindale when examining soils in the area. As a result of his discovery, an investigation was authorised by the Government. Drilling for samples was carried out by Messrs Kear and Waterhouse and Dr Swindale, and the samples were analysed by Dr. Swindale and by Mr J. A. Ritchie of the Dominion Laboratory.