An experimental study of hydrothermal reaction in the system Au₁₀Ag₉₀ alloy-NaHS aqueous solution at 150°C was carried out during 180 days. Reacted alloy samples consist of two parts as inner layer and outer layer.
Outer layer is composed of argentite and inner layer is of argentite and Au-rich electrum (Au₅₉Ag₄₁-Au₆₁Ag₃₉). The formations of argentite and Au-rich electrum are influenced by outward diffusion of Ag⁺ in solution and inward diffusion of S²-in solution. A grain boundary in the starting alloy and a space in the inner layer of the reacted alloy samples are produced by outward diffusion of Ag⁺ in solution. They promoted the reaction of this experimental study. Diffusion rate of Au⁺ in solution in argentite is slow compared with the diffusion rate of Ag⁺. Rate-determining mechanism for the formation of argentite is considered to be dissolution reaction of Au₁₀Ag₉₀ alloy at early stage and that of Au rich Au-Ag alloy at late stage. Diffusion of Ag⁺ in solution at the outer layer and precipitation of argentite from aqueous solution are not ratedetermining mechanisms.

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The Yanomaki metasomatic anorthosite is developed within the Paleogene Ryukoma granite which is composed mainly of biotite adamellite, and crops out in two separate areas (No.1 and No.2 deposits). The shape of each anorthosite body is significantly different, i.e., the body of the No.1 deposit occurs as a sheet, while the body of the No.2 deposit occurs as a dome. These geometries suggest that the former was formed by fracture-controlled alteration and the latter by pervasive alteration. The upper parts of the metasomatic anorthosite bodies are intensely altered to halloysite due to weathering. In some places the metasomatic anorthosite bodies are associated with greisenized zones. Actinolite-quartz veinlet swarms are observed within the No.1deposit. Transition zones between the metasomatic anorthosite and host granite are very narrow; the zone is usually less than 5cm in width.
The metasomatic anorthosite is composed mainly of plagioclase (oligoclase to andesine) and quartz. Minor amounts of titanite and muscovite also present. Actinolite is an additional accessory phase in the marginal zones to the anorthosite. Original K-feldspar, biotite and Fe-Ti oxides have been completely disappeared. The anorthite contents of plagioclase are distinctly higher than those of the host granite. The characteristics of the metasomatic anorthosite can be summarized as follows:
1) Formation of the metasomatic anorthosite took place at a temperature between about 385°C and 644°C as deduced from the metasomatic mineral assemblage and hornblende-plagioclase geothermometry.
2) Original K-feldspar and mafic mineral phases were replaced by oligoclase or andesine. The sodium-calcium metasomatism would be caused by alteration by a high temperature and Ca-rich hydrothermal fluid.
3) The hydrothermal fluid which formed the metasomatic anorthosite was probably derived from a later granitic intrusive situated beneath the Yanomaki mine.

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Sulfide and sulfate minerals in the seven Paleogene coal seams of the Ashibetsu colliery in the Ishikari coalfield, Hokkaido, were investigated by X-ray diffraction of low temperature ash, coal, shale and tuff. The distribution of total sulfur in the coal seams is compared with the occurrence of these minerals and the morphological change of pyrite.
Most of the sulfide minerals found in the Ashibetsu coal seams are pyrite. Marcasite is rare. Pyrite tends to appear near the roof or the floor of the coal seams, and the sulfide and sulfate minerals were not detected in the main part of the coal seams save one, the Torashita-sanshaku seam. In that case, pyrite and gypsum occurred throughout the seam. Total sulfur content is also very low in the main parts of all the coal seams except the Torashita-sanshaku seam. However, total sulfur content is still low in the main part of the Torashita-sanshaku seam at a different location. This evidence suggests that most of the coal seams were formed in a fresh water environment, though a few areas were formed in a brackish water environment. This suggestion is consistent with the depositional environment inferred from the clay mineral composition.
Pyrite exists as very small, microscopically observable crystals even in the coals containing less than 0.5% total sulfur (S). Framboids are rarely present in such low sulfur coals. The number of isolated, small crystals and of framboids increases as S approaches 1%. Bigger framboids and clusters of framboids appear in coals containing more than 1% S. Pyrite spheres, formed from infilled framboids, and larger pyrite spheres or larger, irregular pyrite nodules, formed from infilled clusters of infilled framboids, are often observed in coals containing more than 2% S. All the pyrites of different shapes found in the Ashibetsu coals are syngenetically formed as the result of the activity of sulfur reducing bacteria in different depositional environments.
Gypsum, szomolnokite, conquimbite, roemerite, melanterite, and hydronium jarosite were identified in some coal samples. These sulfate minerals are weathering products from pyrite. Gypsum appears in the early stages of weathering in calcite-rich coal. Iron sulfate minerals appear in calcite-poor coals from an early stage. A coal sample, rich in iron sulfate minerals, was exposed to the laboratory atmosphere for about two and half years, resulting in the appearance of copiapite and paraconquimbite. This indicates that promotion of weathering may cause the iron sulfate mineral phase to be more varied.

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There are reported data about high effectivity complexing of biogeochemistry, biogeophysics (biolocation or dowsing), geophysics and geoarchaeology (the mapping of old pits) in prospecting for blind precious metal-bearing zones, ore bodies and deposits in shutted hilly landscapes of the south taiga and also in geology-structural mapping. The most effective elements of this complex are the nonbarrier biogeochemical exploration (NBE) and the nonbarrier biogeochemical prospecting (NBP). By these methods in the territory where earlier four (4) time were conducted detailed explorations by traditional soil-geochemical and geological methods with digging of 16 magistral buldoser ditches, 100-200 m in length there were revealed 160 supposed ore biogeochemical anomalies (SOBA) of silver, tens of intensive biogeochemical anomalies of gold and 6 platinoids. A re-examination done by digging short 4-10 m ditches of 15 SOBA, having silver content from 100 to 3, 000 ppm, have revealed 9 rich ore bodies with 300-6, 000 ppm Ag, 33 siver-bearing zones containing 1-50 ppm Ag on the background close to 0.1 ppm Ag and also gold-bearing and platinoids-bearing zones. With the help of NBP using crossed net profiles having 1-3 m interval between samples of plants 3 supposed silver deposits with 51, 35 and 15 silver SOBA were identified containing from 70 to 3, 000 ppm in the ash of the nonbarrier bio-objects and having widths of 1-8 m. Complex biogeophysics and geoarchaeology, with resonnaissance biogeochemical profiling is recommended in the first stages of exploration for choosing the prospective localities. NBP combined with geophysical exploration are recommended for contouring of ore bodies and deposits for simultaneous geology-structural investigations on the day's surface.

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Stannite was found in the Otoge kaolin-pyrophyllite deposits of ca. 4Ma(K-Ar), which are localized in rhyolitic pyroclastic rocks of middle Miocene time. Stannite occurs exclusively in pyrite-rich silicified portion within the sericite zone. Under the microscope, stannite, strongly anisotropic, shows a close association with sphalerite and pyrite. Microprobe analysis of stannite reveal that it is of Zn-rich variety with Fe/Fe+Zn atomic ratios of 0.49 to 0.71. It is noted that the atomic contents of the (Fe+Zn) site exceed 1.000 by up to 30% for stannite which contains more than 6 wt. % of Zn, suggesting a possibility of non-stoichiometry. The temperatures estimated based on the Fe and Zn partition are 300°to 340°C with Log f_S2 of ca. -10 to -8, approximately corresponding to the corrected filling temperatures of fluid inclusions in quartz nearby stannite.

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