Samples from 46 deposits of the known 76 occurrences of diatomite in Australia have been micropalaeontologically examined, and 27 genera of diatoms represented by 48 species have been identified from them. The distribution of these species in the various diatomites is given in Table II. The following tentative conclusions with regard to the suitability of Australian diatomites for filtration purposes are based on a study of the shapes and sizes of the contained diatoms,' in accordance with English and Californian experience. Extensive deposits of diatomite, which are dominated by the diatom Melosira and which are suitable for purposes other than filtration, are available in Queensland and New South W ales. Nevertheless, this type of diatomite is used successfully by Davis Gelatine (Australia) Ltd., as a filter medium. The commercial value of a diatomite as a filter aid, which depends on the amount necessary to give a perfectly clear filtrate, the speed of filtration, and the character of the press-cake and similar criteria, can only be satisfactorily determined by actual experiment. It is also necessary to establish a correlation between the characters determined by microscopic examination and actual filtration tests before a final conclusion can be stated.

The oldest rocks found in this area are Pre-Cambrian and the youngest are Recent but on the whole the area is one of great stability and not many of the periods of geological time are represented. The Pre-Cambrian are found outcropping round the edge of the basin and for simplicity in field work have been divided into five divisions. These are Tennant Creek, MacArthur R., Buldiva, Helen Springs, and Barkly Downs. This report provides a field summary of geology by division.

A geological report on the Alexander, Halley's Comet, and Manolis' Workings mines. The production, grade, geology, mineralisation, ore reserves, and prospecting of the mines are discussed. Accompanying geological plans are included.

A request was made for an estimation of the ore reserves indicated to date in the King Island Scheelite Mine, and for a drilling campaign to be drawn up to prove a total of fifteen years supply of ore at an annual rate of consumption of 200,000 tons. These two matters are dealt with in this report.

Results of a micropalaeontological examination of samples taken from a depth of 1,125 feet down to 1,450 feet.

Results of a micropalaeontological examination of samples taken from the depth of 3 feet down to 534 feet.

An examination was made of a proposed dam site at Geehi in April, 1947. The report comprises notes on access, general geology, evidence gathered from aerial photography, and the suitability of the site. Three accompanying plans, and a petrographic report on rocks collected from the vicinity, are appended to this report.

The known bauxite deposits near the township of Ouse are No. 1 on Glen Dhu Estate, Nos. 2, 3,4 and 5 on Gladfield Estate, and Nos. 6, 7, 8, and 9 on Leintwardine Estate, Nos. 10, 11, 12, 13 and 14 on Lachlan Vale Estate and No. 15 on Lawrenny Estate. Examination of all the occurrences and testing of the more promising by shaft sinking and boring was conducted. The results of this work are discussed in the report.

This geophysical survey was undertaken as part of a campaign by the N.S.W. Mines Department and the Commonwealth Bureau of Mineral Resources to explore the ore possibilities of the Cobar Mining Field. Tests, made in January 1947, on specimens of ore from the operating mines showed that some of the ore from the New Cobar and Chesney Mines exhibited appreciable magnetisation due to its pyrrhotite and possibly magnetite content. The survey was commenced in March, 1947 using the magnetic method only as a first method of attack. Watts Vertical Force Variometers Nos. 15887 and 16128 were used, the field work being carried out by the writers. The geology of the area, object of the survey, results, and recommendations for future drilling are discussed in this report. Two accompanying plans are included.

Collie is the only developed coalfield in Western Australia. Between June 1946 and April 1947 a comprehensive geological and geophysical survey was carried out to determine the boundary of the basin, its general configuration and the depth (thickness) of the sediments overlying the basement. The aim of the survey was to define those areas where there was sufficient thickness of sediments to enable drilling to be carried out with a reasonable expectation of proving additional reserves of coal. The geology of the area, application of the gravity method, results and interpretations, and drilling recommendations are discussed in this report.