The velocity of a particle in water depends on both its size and specific gravity. For separation methods, in which separation is done by the difference of particle velocities, such as a jig, a cyclone, or a shaking table, separation by size or specific gravity cannot be completely achieved unless either condition is adjusted to a suitable range in advance. When using the difference of the settling velocity, the size range that should be adjusted before separation is especially called the equal settling ratio. This has only been defined for stationary water, although water movement must be taken into account in the actual separator. In this study, the change of the settling velocity in oscillating water was experimentally investigated for two kinds of particles, which have different specific gravities but the same settling velocity in stationary water, by focusing on the oscillation field which is one of the element movements of a separator. Zirconia (202μm in average) and glass (435μm in average) samples, that are spherical and mono-disperse systems were used. The equal settling ratio becomes smaller while the setting velocities of both samples decrease in oscillating water. That is, the settling velocity in oscillating water becomes more dependent on particle size rather than specific gravity compared to the case in stationary water.

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A fundamental study was carried out on the process for recycling tantalum from off-spec capacitor scraps that are generated during manufacturing process in a large mass. By oxidizing the capacitor scraps in air at 1150K, followed by physical and chemical treatments (e.g., magnetic separation, sieving, and acid leaching), tantalum oxide (Ta₂O₅) powder was recovered from the scrap with a yield of 90% or more. Tantalum powder with 99 mass% purity was obtained by the magnesiothermic reduction of the obtained tantalum oxide powder, and silicon was found to be major impurity in the tantalum. A new purification process for tantalum, utilizing chloride wastes generated from the titanium production process, was also investigated and thermodynamically analyzed from various aspects. Furthermore, it was experimentally proved that metallic tantalum can be chlorinated by iron chloride (FeCl_x), which is a major chloride compound in the chloride wastes from titanium smelting process, and that iron-free tantalum chloride (TaCl₅) can be produced. The results obtained in this study demonstrate not only the effective purification process and recovery of tantalum but also the possibility of recovering chlorine from the wastes generated during the titanium smelting. The investigated process of recycling chloride wastes may be useful and applied to other metals, because it has the potential for reducing the chlorine loss caused by chloride waste generation in chloride metallurgy.

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In the last decade, from around 1990 to 2000, movement of merger and acquisition in the world mining industry was activated in accordance with the globalization of the world economy. This study discusses the issues related to the world copper mine production and changes on the mining technologies during this decade.
At first, trend of world copper production and consumption was analyzed, then technology tendencies in this decade was discussed with the results of the research and analysis on the world newly developed copper mines. Mine technologies, put to practical use in this decade, were picked up.
The main points resulting from the study include:
- production from openpit mines were increased, and enlargement of the mine size as well as cost reduction is remarkable,
- efficiency of the mine operation employing larger machinery and facilities to handle large amount of ores is one of the key factors of mine technologies,
- IT is rapidly facilitated to the mines and mills for reducing operation costs and the efficient control, and
- SX-EW production of copper mine is remarkably increased and it is considered that a production technology, such as hydrometallurgy for the primary sulfide copper ore, which enable metal production at mine site should change the mining industry in future.

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Worldwide nonferrous metals exploration activities had changed drastically in 1990's. From early 1990's to 1997, the exploration budget steadily increased due to the high metals prices and privatization of mining sector in developing countries. However, the drop in metals prices in 1997 caused to fall the exploration budget, and this downturn continued until 2002. Here, 14 base metal companies are focused and their detailed exploration activities are clarified from late 1990's to 2003.

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This paper reviews the development of remote sensing, geophysical and geochemical techniques, and their application to mineral exploration over the last decade in addition to introducing the related research and development works by the Metal Mining Agency of Japan (presently Japan Oil, Gas and Metals National Corporation). In the field of geologic remote sensing, ASTER data with high spatial and spectral resolutions is widely used as well as conventional satellite data such as LANDSAT and SPOT data. Airborne data acquisition with either optical or radar sensor is commonly used. Hyper spectral data acquisition has also been developed both in satellite and airborne systems. Geophysical techniques are versatile using airborne, ground and drill-hole methods. In gravity, magnetic, electric and electromagnetic methods, several techniques have been developed in data acquisition and analysis. Airborne gravity method has been recently developed and started to be used in exploration. Though the geochemical techniques are still based on conventional methods employing rocks, soils and stream sediments, better understanding to the geochemical phenomenon has greatly improved interpretation of the results. Regolith mapping method, which was resulted from research work for the deeply weathered tropical terrain, is one of the good examples. Exploration manager is required to follow the more advanced mineral exploration techniques and apply the most suitable combination of the methods to the project in response to the exploration stage.

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The Japan Oil, Gas and Metals National Corporation (JOGMEC), a non-profit Incorporated Administrative Agency, succeeded all the overseas exploration programs of former Metal Mining Agency of Japan (MMAJ) on February 29th, 2004. A wide range of exploration activities from grass-root to pre-feasibility in both developed and developing countries are conducted for assisting and encouraging Japanese companies for their upstream projects in contribution to stable supply of nonferrous metals.
Overseas exploration program of JOGMEC currently consists of three categories: (1) 'Overseas (Joint) Geological Surveys' which directly assist mineral exploration activities by Japanese private companies; (2) 'Technical Cooperation for Mineral Exploration: Government-to-Government Surveys (GG Surveys)' which mainly intend to transfer Japanese exploration skill to governmental organization in developing countries and (3) 'Joint Basic Exploration Scheme (JBES)' which is a joint venture exploration program usually under a farm-in agreement to acquire equity interest of the properties from overseas public or private corporations in developing countries. Such equity interest by JBES will be transferred to Japanese private companies for further explorations and development.
Recent three successful exploration projects are introduced to show JOGMEC's approach and contribution. The Stone-boy project, Alaska, a large grass-root regional exploration program, delineated Pogo gold deposits of 9.9 Million tones with average grading 14.1g/t Au which is planned to commence production from 2006. Two GG surveys of the Kokpentinskaya placer-ilmenite deposit in Kazakhstan and the Dong Pao rare-earth deposit in Vietnam, successfully expanded their original geologic ore reserves nearly double to be a positive economic valuations.
As a future perspective of JOGMEC's metals survey, the JBES will be the most efficient survey program due to realizing both flexibility in project selection and security of tenure in the area of interest.

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The Metal Mining Agency of Japan has carried out a four-year Technical Development project on Disposal Free Treatment of Secondary Fly Ashes from Municipal Waste Incineration. We have attempted to apply the MF (Mitsui-type blast Furnace) process, which is employed to treat electric arc furnace dust, to recover heavy metals contained in the fly ashes along with decomposing dioxins to produce a slag which could be used for cement production.
The main results of our experiments are as follows;
1) Approximately 90% of heavy metals (mainly zinc and lead) contained in the secondary fly ashes can be recovered as raw materials, thereby contributing to non-ferrous metals production,
2) The slag generated from the secondary fly ash treatment using the MF process can be used as a raw material for cement production, thereby utilizing decontamination technology without landfill,
3) Two stages of alkaline washing will be needed to avoid equipment erosion caused by chlorine contained in the fly ashes, and
4) The ratio of decomposition of dioxins is above 99%.
Since 2003, based on the results of this project, Miike Smelter Co., Ltd., subsidiary of Mitsui Mining & Smelting Co., Ltd. has been treating fly ashes from municipal waste incineration at the MF plant in Omuta city, Fukuoka prefecture, Japan.

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In this study, operating costs of mine drainage treatment plant in Japan were analyzed by using the Japan Oil, Gas and Metals National Corporation (JOGMEC) database, and the effectiveness of the technologies developed by MMAJ/JOGMEC was evaluated.
Mine drainage treatment cost analysis showed that,
-the unit operating cost (yen/m³) of the plants on ferrous mine drainage correlates with both the volume of treatment water (m³/min.) and the acidity (CaCO³ mg/L).
-it is possible to make trial calculation on the change of annual treatment cost depending on the change of treatment water volume and the change of acidity.
The technologies developed, so far, by the former Metal Mining Agency of Japan (MMAJ) and the JOGMEC were evaluated in view of effectiveness. The results showed that the vegetation technology, tunnel plugging technology, sludge backfill technology, and sludge densification technology were most effective.
This study provided a basic data set to consider more effective ways on mine drainage control and treatment, but still the data to be improved.
It is recommended that more detailed mine drainage data and analysis is required to improve technologies to prevent and treat the mining related pollution.

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The paper describes the first attempt of introducing paste backfill in Japan at the Toyoha mine. In 1997, the Metal Mining Agency of Japan (MMAJ), which was reorganized in February of 2004 and currently works as the Japan Oil, Gas and Metals National Corporation (JOGMEC), launched a five year long research program to innovate mining technologies and systems required to save and efficiently use energy in mines. As a part of the program, studies on paste backfill technology and its implementation in Japan were involved.
The Toyoha mine was selected as the site for testing paste backfill, since the mine is being operated under an extremely high rock temperature environment. In order to improve the underground climate, the mine decided to introduce paste backfilling and effectively reduce heat flows from mined-out stopes.
The first flow test was performed on surface in 1998 and the second flow test was carried out underground in 2001 after having installed the paste fill plant and underground pipelines. The underground test was, however, abruptly discontinued by a mechanical failure, which happened to the PPSM thickener whose bolts holding the drive head at the top of the thickener were broken.
After the unpredicted interruption of the paste backfilling test, we have carried out a series of ventilation analyses to evaluate the energy saving effects with paste backfilling under a high rock temperature condition. And we have clarified that remarkable energy saving can be expected by reducing heat flows from mined-out stopes and energy consumption required for underground refrigeration. In addition, it is found that significant cost saving can be also anticipated by curtailing volume of the tailings impoundment and its construction cost.

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