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Diatomite. —From deposits at Kamo, Ngongotaha, Ngakura, and Middlemarcli a total quantity of 436 tons of diatomaceous earth was produced in 1947, as against 348 tons in 1946. The material is employed for concrete, plaster, and lagging work, but so far the grade that could be used for filtering purposes has not been obtainable in New Zealand. Dimension Stone.—Stone for building or monumental work was produced to the extent of 14,528 tons during 1947, this total being made up by 122 tons of Coromandel granite, 73 tons of Bluff granite, 2,932 tons of Oamaru building-stone, 440 tons of marble from Hammer, 148 tons of sandstone from Charteris Bay, Lyttelton, and 10,809 tons of blue stone from quarries at Christchurch, Oamaru, Balclutha, and Dunedin. Salt.—An entirely new departure in mineral-production is at present in its initial stages at Lake Grasmere, in the Marlborough District, where it is planned to produce salt by the solar evaporation of sea-water. The low rainfall, long hours of sunlight, and the wind conditions make this locality the most suitable one in New Zealand for this purpose. The company has now about 1,200 acres of the lake area enclosed and covered with sea-water, and the intake from the sea, complete with pump-house, was completed, last January. Accommodation for staff has been erected and a road of one and a half miles across the lake constructed between the company's headquarters and the intake. Samples of salt have been already collected, and possibly some salt may be harvested this year. General. —Small amounts of quartzite and fuller's earth were produced during 1947, while there was also production in some quantity of rock for harbour-works, sand, gravel, &c., for roads and ballast, sand, &c., for building aggregate, stone dust for coal-mines, &c., and limestone for industrial uses. GEOLOGICAL SURVEY Regional geological survey is being carried out as far as pressure of work permits. Field-work was completed in Motatau Survey District (North Auckland), in Wanganui Subdivision, and in North Otago. It is proceeding in Punakitere Survey District (North Auckland) in the " mineral belt," Nelson, and in West Southland. The coalfields of North Auckland, Reefton, Greymouth, Murchison, South Otago, and Southland have been under investigation continuously, and the latest information from field-work, drill-holes, and mining has been compiled, tested, mapped, and used to guide further work. Water-supplies have been reported on at Whangarei, Auckland, Cambridge, Three Kings, Rotorua, Rangitaiki, Wairakei, North and South Canterbury, Timaru, Waikouaiti, and Southland. Quartzite and greensand have been mapped near Paraparaumu. Glass-sands have been sampled from Parengarenga, Helensville, and Mount Somers ; bentonite and pozzolana in the Wairarapa and East Coast districts ; and diatomite has been examined near Taumarunui and Hawera. Dams, tunnels, roads, quarry-sites, &c., have been reported on for Government Departments and local bodies. From the field geologists, Government Departments, local bodies, prospectors, &c., rocks come in continuously and are tested and reported on by the penologists. Considerable attention has been directed to rock aggregates for cements, with reference to those liable to react injuriously. Volcanological work has proceeded in the Rotorua-Taupo region, and investigations have been made into the utilizing of steam and hot water for heating and power purposes.

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