The writer has intended to clarify the sources of error in ore reserve estimation, because the subject has been of considerable interest to mining geologists as well as to miners, and only a little analytical work has been done on the it in Japan.
As the first step, the precision of the estimates of the amount and grade of ore which had been mined in certain blocks of several mines in Japan, was examined from the standpoint of sampling methods, as these estimates had been based on the results of underground stope sampling. Then the precision of the estimates of the ore reserves was roughly evaluated on the assumption that the sampling method corresponds approximately to the case of two-stage sampling where the sample size of the first stage is only two.
The average, variance, etc. are calculated in the dimensions of t/m ² for ore reserves and kg/m ² for metal content. The values of standard error/average of metal content are approximately 0.1 to 0.2.
The precision of measurement and calculation required in comparison with the "sampling error"is such that all values (amount of ore reserves, metal content, and assay) may be rounded off to two or three significant figures.
Preliminary study on the size of each increment was also given.
This study gives only approximate results insofar as specific numerical values are concerned.

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The problem of material-transfer in the course of wall rock alteration is discussed in relation to diffusion. The actual features of distribusion of the heavy metals such as lead, silver, chromium, nickel, and vanadium were compared with the theoretical features, and it was determined that solute diffusion may be most important in the transfer of elements.
The rate of the migration of elements in some geologic environments is also discussed.

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The area surrounding the Nodatamagawa mine consists of Palaeozoic, Late Jurassic, and Pleistocene sediments, and granitic rock which intrudes and thermally metamorphoses the Palaeozoic sediments, and is overlain by the younger sediments.
Manganese ore deposits are distributed in a quartzite zone of the Palaeozoic sediments, and a schematic succession of phyllitic quartzite, manganese ore body, massive quartzite, and phyllitic quartzite is. apparent from the foot wall side to the hanging wall side. Many kinds of manganese minerals have been identified; hydroxides and oxides occur in the inner part and silicate minerals occur in the outer part of the ore body.
The uraniferous ore deposits develop in the Palaeozoic sediments and are classified into two types, a vein type and a bedded type. The vein type deposit occurs along faults and fractures which are concordant or discordant with the strata. The typical uraniferous veinlet includes molybdenite, pyrite, cobaltite, and gersdorffite, besides uraninite. The bedded type deposit is uraniferous hornfels that is. confined to a definite stratigraphic horizon. It is generally distributed between the massive and the phyllitic quartzite mentioned above. The hornfels is characterized by a remarkable abundance of sulphide and arsenide minerals, which occur generally as impregnations and/or streaks along the bedding plane. The uranium content of the entire hornfels body is estimated to be 0.01% or less, though uranium is locally concentrated in amounts up to 0.15%. Uraninite shows a close association with pyrite in the streaks, and the major part of the uranium occurs in biotite as very tiny uraninite with a diameter of 1-2μ. The ore minerals in the hornfels are pyrite, pyrrhotite, chalcopyrite, sphalerite, and nickel-cobalt minerals such as niccolite, gersdorffite, pentlandite, and cobaltite.
Analysis of several samples shows that arsenic, cobalt, molybdenum, nickel, and vanadium are abundant trace elements. The carbon content is less than 3.25%.
The writers conclude that a syngenetic origin of uranium in the hornfels is more likely than a magmatic origin related to the granitic rock. It is also conjectured that the uranium in the vein type deposit may have migrated, been redistributed, and concentrated from the uraniferous hornfels.

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The Yakuki mine is one of the typical pyrometasomatic copper deposits in Japan, and is situated in the eastern area of the Abukuma mountain range. The ore deposits are distributed widely in a skarn zone along the foot wall of a thick limestone bed of the Paleozoic formation. Localization of the ore is controlled by the folds of the host rocks, which might have been caused by later igneous intrusions. Ore minerals are zonally arranged from west to east, replacing the skarn minerals, but the pyrrhotite seems to have replaced selectively the impure part of the host rocks, especially limestone.

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The Inakuraishi Mine is located in the central part of the Shakotan Peninsula, southwestern Hokkaido, and works manganese ore. A Neogene Tertiary formation is extensively developed around the-mine. The formation is divided into four groups : tuff breccia, propylite, propylitic agglomerate, and tuff interbedded with some thin shale beds.
The ore deposits belong to an epithermal fissure-filling vein. The vein systems are summarized as follows:
1) N55°W, 75°N……Mansei-hi
2) N75°E, 70°S……Kinsei-hi
3) N80°E, 75°N or 75° S……Many branch veins of Mansei-hi and Okuinakuraishi-hi
The Mansei-hi and Kinsei-hi consist of several veins of different magnitude, the former being the main vein of the mine. Judging from the modes of occurrence and natures of veins, it is concluded. that the fissures filled by veins of the Mansei-hi are shear fractures, and those filled by veins of the Kinsei-hi are tension fractures, formed by a N 75°E stress acting on the mining area.
This ore deposits consist mainly of rhodochrosite with some sulphide minerals. The ore is classified into the following two types:
(a) deep rose-colored rhodochrosite ore
(b) light rose-colored rhodochrosite ore
Ore of the type (a) contains about 0.1—0.2% Fe whereas that of type (b) contains 1.5% or more Fe. Such difference in the ores is due to the chemical composition of the contained rhodochrosite. The light rose-colored rhodochrosite is of an earlier stage than the deep rose-colored rhodochrosite.
The wall rock alteration is characterized by chloritization, silicification, argillization, pyritization, sericitization, albitization, and carbonatization. Argillization is observed in the extremity of the vein.
Three altered zones can be distinguished in the wall rock of the Kinsei-hi on the basis of mineralogical assemblages, as follows:
1) Quartz-sericite zone, (2 meters on both sides of the vein)
2) Sericite-quartz zone, (from 2-30 meters on both sides of the vein)
3) Chlorite-quartz-albite zone, (beyond 30 meters on both sides of the vein)

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