The Dong Pao rare earth deposit is located in a mountainous area of Northern Vietnam, associated with Paleogene alkaline granite intrusion. It was discovered in the late 1950's, and has undergone exploration since then. In the 1980's, a calculation of the ore reserve for the main ore deposit and an outline of the exploitation plan were created by the Vietnamese government. In the 1990's, small scale mining of fluorite was conducted. However, despite a cooperative study by the MMAJ in 2001-2002, there has not been actual development of rare earth mining operations. This is mainly because of technical problems with ore minerals processing.
By the request of the Sojitz Corporation, the authors re-analyzed the existing data and carried out additional surveys of the F3 ore body, one of the main ore bodies at the deposit. Based on the chemical compositions of the rare earth elements and cerium anomalies, zonation in the depth direction was detected, which is associated with weathering, and the ore types in the zonation were classified.
The results of oxygen and carbon isotope measurement and geological observation of host rock beneath the ore body show an unusually high grade rare earth deposit (TREO=10%) formed in association with possible carbonatite, by lateritic weathering of carbonatite ground. It was indicated that bastnaesite, fluorite, and barite would be weathered residues and concentrates.
Using high-grade soft ore from an un-oxidized zone in the regolith, a systematic processing test for gathering bastnaesite showed good results and technical prospects for development. Pit design and an overall mining plan to target recoverable ore at the F3 pit became considerations.
Based on these study results, the Japanese enterprises and organization are jointly intends to conduct Feasibility Studies.

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Rare metals are necessary for frontier industries of our country. The Ministry of Economy, Trade and Industry of Japan has its policy of supply stabilization of rare metals. Vanadium, one of rare metals, is used as adding agent for molten steel. 90 % of vanadium consumption in Japan is for usage as adding agent. The price of vanadium is very sensitive for production in Russia, China and South Africa. Vanadium is one of nine rare metals of national stockpiles which is essential for national industries in Japan. However, there are no records of recovery of vanadium from domestic resources. The survey of vanadium resource in the country has not been executed in the past.
We studied vanadium resource in iron sand deposits along the Pacific Ocean coast, southern Hokkaido and eastern Tohoku area by compiling chemical data in the reports of unused iron resource survey in Japan, which were conducted from 1954 to 1959, followed by sampling survey. V₂O₅ grade in iron sand samples was generally from 0.12 to 0.16 % at Sahara area, Hokkaido and Ushikawa area, Aomori. The maximum V₂O₅ grade in iron sand showed 0.44 % at Sahara area, Hokkaido that was nearly same grade as general vanadium ore. We clarified that vanadium in the iron sand resources of our study area was assumed to be originated from Ti magnetite. The decrees of liberation of Ti magnetite were 63 to 71 %. Thus recovery and grade of vanadium was thought to be improved by using Low Intensity Magnetic Separator (LIMS). Possible recovery of V₂O₅ in Sahara area, Hokkaido, was estimated 781 ton by using recovery rate of 63% in accordance with our study. This V₂O₅ amount is equivalent to 30 % of Japanese annual import 2,500 ton. The estimated resource of iron sand in Hokkaido is 43 million ton. Thus we estimate that vanadium resource in iron sand is considerable amount in Hokkaido.
Iron sand deposits with high content of vanadium are located widely in our country. The study indicates possibility of contribution for stable supply of vanadium resource by recovery from iron sand resources in Japan.

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Experiments on the cerussite (PbCO3) - aqueous NaHS solution system were performed at 150°C. Scanning electron microscopic observations of run products revealed the formation of large hexagonal and small granular crystals of galena replacing cerussite. The replacement texture of cerussite by galena progressed toward the inside of cerussite without recognizable change in the form of the sample after the reaction, hence being was classified as a pseudomorphic and guided penetration replacement texture. It is reasonable to assume that cerussite is replaced easily by galena because the molar volume ratio of replacing mineral (galena) to replaced one (cerussite) is 0.78, and a large volume of void space was formed in the galena replacing cerussite. Our results also suggest that the replacement of cerussite by galena can be achieved if the NaHS concentration in the solution is sufficiently high (1.0 mol/L). The diffusion of solute species is thought to be the rate-determining process for the metasomatism for the chipped cerussite sample in 0.1 mol/L NaHS solution system. The diffusion constant D value for this case is approximately 3.0×10^-9 m²/s. On the other hand, the dissolution is the rate-determining mechanism for the chipped cerussite sample in 1.0 mol/L NaHS solution system in the initial stage within about 1 day, while the diffusion is thought to be the rate-determining mechanism after 1 day with the D value of approximately 7.7×10^-8 m²/s. The dissolution rate constant k for cerussite dissolution in the metasomatism for the powdered cerussite sample is approximately 7.3×10^-8 and 1.2×10^-6 mol/m²s for NaHS concentrations of 0.1 and 1.0 mol/L, respectively.

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Feeding ores and tailing slime from Pb-Zn deposits hosted in rhyolites and carbonates-rich sedimentary rocks were studied chemically by ICP/MS. The rhyolite-hosted one at Na Son is rich in Pb (Pb/Zn=4.1), and also rich in such chalcophile elements as Cd, In, Cu, Co, Ni, Bi, Ag, Sb and Se. Important pollutants of Pb, Cd and As are well decreased in the tailing slime. REEs contained as cerianite are all moved to the tailing slime.
Pb-Zn ores from the Cho Dien sedimentary area are rich in chalcophile elements such as Cd, In, As, Ag, and also Fe. Recovery rates of the flotation are high in the Zn (58%) and thus Cd (64%), and also lead (92%). Arsenic and iron are high in both the feeding ores and tailing slime, implying these are contained as arsenopyrite and transported to the tailing ponds. Pb-Zn ores from the Lang Hich sedimentary area have high Zn/Pb and Cd/Zn ratios, but are poor in chalcophile elements, and Fe and Mn. About 87 % Zn and 88 % Cd of the ores are recovered by the flotation. Arsenic and Fe are originally low with averages of 185 ppm As and 1.15 %Fe; all moved to the tailing pond.

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