The bedded limonitic iron-ore deposits found in Japan are genetically classified into two major types, i. e., the hypogene type and the supergene type. Furthermore, the hypogene type may be subdivided into the simple hypogene and the complex hypogene type, and the supergene type may be subdivided into the secondary-enrichment supergene and the concentration supergene type.
Though all the ores from any of these deposit types are mainly composed of goethite, the types are characterized by the minor elements. Some of these elements are useful as indicators in prospecting for iron-sulphide deposits under or near the limonitic iron-ore deposits.
Around many volcanic craters, the following zonal arrangement can be observed outward from the center : solfatara, sulphur deposits, strongly acidic hot springs, limonite deposits of the simple hypogene type, ferruginous springs, moderately to weakly acidic hot springs, and neutral or weakly alkalic hot springs. This arrangement is a useful geologic tool in discovering new limonite deposits of the simple hypogene type.
As plants-particularly the living bryophyta-are considered to play a more important role than ironbacteria, the writer describes the mechanism of iron-ore deposition from the botanical point of view.
The limonitic iron-ore bed of the Kamikita mine was sampled systematically along the Okuno-sawa valley. This bed is of the secondary-enrichment supergene type. The samples were analyzed spectrogr-aphically for minor elements, and the behaviour of these elements is explained from the viewpoint of their ion-potential.

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The main ore deposit of the Shirataki Mine is a cupriferous pyritic bedded ore deposit. The mine is in the Sanbagawa crystalline schists of Central Shikoku.
The geology of this district consists mainly of alternating layers of spotted black schist and spotted epidote-hornblende schist accompanied by spotted piedmontite-quartz schist and spotted sandy schist. These rocks are characterized by the presence of albite porphyroblasts.
Usually the "phyllitic green schists" are developed around cupriferous pyritic ore bodies in this mine, and it has been said that these highly schistose rocks were altered from spotted epidote hornblende schists at the stage of fissure filling mineralization after the recrystallization of country rocks was nearly completed. The main constituent minerals of the "phyllitic green schists", however, are green hornblende, chlorite, sericite, epidote, albite, quartz and a carbonate mineral. Chloritization of green hornblende at the mineralization stage is not observed in these rocks, and green hornblende and chlorite show an equilibrium relationship during the regional metamorphism.
As a result of fabric analysis of the S-surface and lineation, it seems possible that the layers in this district were controlled by two main stages of foldidg during one cycle of kinematic movement, and the layer of the "phyllitic green schists" within ore bodies chiefly influenced by folding of the later stage.
It appears that the metamorphic facies of the rocks that include the "phyllitic green schists" corresponds to the epidote amphibolite facies.

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The Fujigatani Mine is one of the important scheelite-ore deposits of contact metasomatic origin, and is located in the Kuga district, Yamaguchi Prefecture.
The Palaeozoic formation consists of slate, chert, sandstone and lenticular limestone, and is intruded by dikes of aplite, liparite and lamprophyre. In the southern region of the district, biotite granite crops out and argillaceous sediments are converted to spotted slate or biotite hornfels as a result of this batholitic intrusion.
The ore deposits can be classified into the following two types:
1) Contact-metasomatic massive ore deposits
2) Scheelite-quartz vein ore deposits
The main ore deposit consists of four groups, and many ore bodies in each group are arranged parallel to the fold axis. As the form of the ore bodies is clearly controlled by geologic structure, the slip plane (S) and lineation (L) of the country rocks or limestone bodies, the direction of the ore shoots and variation in thickness of the ore bodies can be determined geologically.
The writer analyzed them by the "L-S Fabric Analysis" method presented by R. Sugiyama to analyze the fabric inwoven by lineation and the schistosity plane of the rocks. The chief constituents of the contact-metasomatic ore are scheelite, associated with chalcopyrite, pyrrhotite and other sulphide minerals. The skarn minerals are garnet, diopside, hedenbergite and quartz.
Scheelite-quartz veins are observed in joints or minor slip planes, and are younger than the contact-metasomatic deposits.
The tungsten content is especially high where these scheelite-quartz veins cut the skarn mass. Joints or minor slip planes are considered to be tension cracks normal to the fold axis of the area.

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During the half century, since the Hitachi mine was first developed, most of its geologic relations have been discovered. Recent studies by M. Shimada and his colleague have given many results, important from both scientific and economic aspects. Some problems introduced by the advance of science, however, still remain.
First, the geologic age of the formation surrounding the mine has been alluded, as a whole, to the Lower Carboniferous. The discovery of Permian fossils in the limestone pebbles of the Tertiary conglomerate overlying the formation, was introduced the possibility of a Permian age for a part of this formation.
Second, the Paleozoic formations have been thought to be monoclinic, until M. Shimada ascertained an overturned synclinal structure in the country rocks of the ore deposits. This aroused a new concept of repeated folding, the exact nature of which is still to be investigated.
Third, the irregular shape and arrangement of the deposits on the southwestern part should be investigated in relation to this folding, not on the concept of a mere local disturbance.
Fourth, a new assumption that the ore deposits have been formed by the following stages requires consideration in relation to the fundamental geologic history of the area.
1. The original ore deposits were formed in association with preorogenic volcanism, perhaps in the Carboniferous.
2. Reformation of ores into fine-grained granoblastic aggregates, arranged concordant to the schistosity of the wall rocks, was caused by an orogenic movement accompanied by a minor concordant intrusion, perhaps at the end of the Permian.
3. Parts of the ore were further converted into irregular bodies of high temperature aggregates by a post-orogenic discordant intrusion of granitic magma, perhaps in the Mesozoic.
Material migration during metamorphism is also considered from a new standpoint.

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