The opal industry in Australia has experienced a marked revival during the past few years, and the value of production during 1946 was the highest recorded for 40 years. To some extent this is due to the purchases made by American troops when they were stationed in this country during the war, and the publicity given to the gems when the troops returned to their homes. Apart from the direct effect of this publicity on the demand for tl1e gem, the discovery of good stone in a hitherto unprospected portion of the principal field led to considerable improvement in production. It is frequently pointed out that Australia is the principal opal-producing country in the world, and that this pre-eminence should enable us to exercise what amounts to international control of the industry. Whilst there are cogent arguments against any attempt to establish world control, a good case may be made for a greater degree of economic stability in the industry within Australia. The possibility of devising a method which would be in the best interest of all sections of the industry was investigated by the Bureau of Mineral Resources, and the results of the inquiry form the subject of this Bulletin. It is appropriate to emphasize several points which must be kept in mind if the opal industry is to be considered in its proper perspective. As far as can be ascertained there is no commercial use for opal other than as a gemstone, and it must, therefore, be regarded as a non-essential luxury item. Although opal may have a considerable value as an export commodity, the industry is subject to vagaries of fashion and other unpredictable factors which make stabilization extremely difficult. Besides this disability is the relative insignificance of opal production compared with that of other minerals on the basis of recorded value it constitutes less than 005 per cent of the total 8 mineral production in Australia. It should be clearly understood, therefore that a small non-essential industry is under review, and any departure from this perspective will lead to misunderstanding of the views expressed in this Bulletin. For these and other reasons it will be understood that values of production quoted in this Bulletin must be regarded as comparative rather than absolute, and it may be safely assumed that they are all under-estimated. The remainder of this Bulletin is divided into two major parts-the first dealing with the raw material, and the second dealing with the marketing aspects and a discussion of the various methods which have been suggested for stabilization of the industry. Emphasis throughout is on the present rather than the past, although some historical data are included as essential to a proper appreciation of the present circumstances in the industry.

The writer received instructions to commence the geological mapping of the Port Moresby area with special attention to economic aspects, such as, raw materials for the manufacture of cement, materials for concrete aggregates, road surfacing materials, etc. This work was commenced on November, 30th, 1949, and a general rapid reconnaissance of the more readily accessible areas carried out.

This report describes the results of a micropalaeontological examination of rock samples from the lower Minilya area.

The following is a summarised account of an investigation into the heavy mineral content of thee bores (Nos. 2, 3, and 4), put down by the Roma Blocks Oil Company. The positions of the bores and a short account of the geology of the area are given, together with results of the work to date, and an evaluation of the prospects of correlation by petrological means.

The primary aim of the investigation was to determine the reserves and distribution of monazite in the deposits of heavy mineral sands along the East Coast. These deposits contain most of the known world reserves of zircon and rutile for which they are being exploited at various localities, mainly from North Stradbroke Island in Queensland to Ballina in New South Wales. Monazite forms little more than 0.5 per cent of the mixed concentrates, but can be recovered as a by-product from the separation of the other minerals. The monazite forms a source of supply of cerium and also of thorium. The thorium content of the monazite is determined on the basis of its radioactivity. This report gives an account of the field and laboratory work carried out. The results of the laboratory work, which included the separation and examination of minerals, the radiometric determination of quantities of monazite, and the investigation of the thoria content of monazite, are described in this report.

Previous investigators in the area have interpreted the Nerrima Dome as a dome closed by folding (Wade, 1936), a dome closed against a transverse fault at the eastern end (Kraus, 1942), and as a westward plunging anticlinal fold probably closed by transverse faulting (Reeves, 1949). The purpose of the present survey is to determine by detailed geological mapping the true structure of the Nerrima Dome.

A sample of diatomite was submitted for palaeontological examination. The results are of the examination are recorded in this report.

Rock sample from six localities in northern Australia were submitted for macropalaeontological examination. The rock samples and their fossil contents are described in this report.

A sample of diatomite was submitted for palaeontological examination. The results are of the examination are recorded in this report.

This is the second progress report of the coal drilling programme near Ashford in the Parishes of Macdonald and Myall, County of Arrawatta. The first report (Record 1949/106) covered the drilling of D.D.H's 1-5. Drilling was continued to test the coal measures lying between old Ashford Colliery and the Severn River. Five more holes were drilled through the coal seam, north of No. 2 D.D.H. An account of the drilling work is set down in this report, together with a description of local geology, and estimates of the coal reserves in the field.