Skarn-type tungsten ore deposits of the Kiwada mine are located at Futashika, Iwakuni City, Yamaguchi Prefecture, western Japan. The area is underlain by the Triassic Kuga formation which consists of mudstone, chert, sandstone and limestone. The formation is intensely folded into anticlinorium and synclinorium trending east-westerly, and is metamorphosed to biotite or spotted biotite-cordierite hornfels by the late Cretaceous granitic intrusion.
The mineralization which replaces the limestone of the Kuga formation is thought to be related to the granitic activity. Some fifteen orebodies of varying sizes from 200t to 80, 000t, in which the grade ranges from 0.5 to 7.0% in WO ₃, have been found to date. Tungsten mineral is exclusively scheelite with a minute exceptional occurrence of wolframite which appears to be pseudomorph after scheelite. The skarn of the deposits consists of such minerals as garnet, clinopyroxene, wollastonite, vesuvianite, epidote, plagioclase, muscovite, chlorite, quartz and calcite, and is rather commonly cut by quartz veins. Scheelite occurs both in the skarn and the quartz vein, but the highest concentration is seen in and around the quartz vein that runs amid the skarn body. In larger orebodies there remains some limestone in the core which is surrounded successively by the zones of wollastonite-vesuvianite, quartz-calcite and clinopyroxene-garnet. Major sulfide minerals found in the orebodies include pyrrhotite, .chalcopyrite, arsenopyrite, pyrite and sphalerite.
Localization of orebodies seem to be controlled by two structural factors: (1) folding axes of the Kuga formation which define the possible site of limestone lenses and (2) tensional fractures crossing the folding axes at nearly right angles which provide the paths for ascending ore fluids. The limestone lenses cut by quartz veins filling the above fractures are therefore the targets of search for high grade ores. As the limestone in the area is generally very small in scale and is seldomly exposed, bore hole exploration based on the detailed geologic data seems to be the sole promising way of searching new orebody and has been quite successful in the past few years. Underground S. P. measurement and the magnetic survey with a proton magnetometer have also been found useful in the case of locating the hidden orebodies within relatively short distances (5-10 meters).

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The Campo Formoso area is well known in Brazil as a locality of chromite occurrences since the end of the 19th century and the chrome ore has been produced in a comparatively large scale since the early 1960s by FERBASA mainly from the Pedrinhas mine. The prospected area during three years from 1972 by the Companha Mineracao Serra da Jacobina (SERJANA) is located east to the Pedrinhas mine and is about 110km² in area which corresponds to the expected narrow serpentinite zone occupying a part of the west margin of the Serra da Jacobina.
The geology of the peripheral district of the Serra da Jacobina is composed of Caraiba group, sepentinite, Jacobina group, gneissose granite and later granite of Precambrian in age. The Caraiba group, composed of gneiss, migmatite, schist as well as ultramafic complex or single ultramafic body, together with gneissose granite and later granite forms a gently undulating peneplane. The Jacobina group, mainly composed of psamitic, pelitic and conglomeratic sediments and metamorphosed to the amphibolite facies, forms the Serra da Jacobina of about 200km in N-S length and under 10km in width elevating under 300m above the peneplane and thrusts up the Caraiba group on the west side of the Serra da Jacobina. The chromitite bearing serpentinite composed mainly of serpentinite accompanying partly pyroxinite, hornblendite and talc schist occurs below the above-mentioned thrust and forms a colluvial slope below the escarpment of the Jacobina group. Though it is continuous from the Cascabulhos area to near Campo Formoso about 20km in entire length and under several hundred meters in width, it becomes thinner and lenticular northward. The age of this serpentinite is thought to be prior to the Jacobina group because of the presence of burried chromite placer deposits in the latter.
In the Limoeiro area, almost southwesternmost part of the prospected area, two layers of chromitite occur in the serpentinite-saprolite and are characterized by predominant friable low grade ore and scarce high grade lump ore, which are common to the already known other deposits in the area. Also, some detrital chrome deposits occur on the colluvial slope.
The Limoeiro mine was placed in operation in 1977 and 82, 000 tons of chromite lump and concentrate were produced.

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The minerals of the scheelite-powellite series containing 0, 0.5, 1, 2, 4, 6, 10, 20, 40, 60, 80 and 100 mole % CaMoO₄ have been synthesized. The solid solution of this series was obtained by the slow addition of a Na₂WO₄-Na₂MoO₄ solution to a large volume of boiling CaCL₂ solution. The fluorescent colors of the precipitate change as follows: blue at the scheelite end, pale blue at 0.5 mole % CaMoO₄, white at 1 mole %, pale yellow at 2 mole %, and yellow at 4 mole %; and increase yellow tint up to 20 mole %, but do not show any remarkable change beyond that composition. Compared with the standard color card (Fig. 4), on which the precipitates are put, the composition of scheelite containing less than 10 mole % CaMoO₄ can be determined within the accuracy of 1 or 2 mole %.
The X-ray powder data show that the 2θ ₁₁₆ (CuKα)-2θ₂₂₀ (CuKα) values decrease linearly from 5.23° to 4.83° with the increasing amounts of powellite component in this solid solution. Using this value, the composition can be estimated within the accuracy of 10 mole % CaMoO₄. From the synthesis, fluorescent colors and X-ray data, it is inferred that the solid solution of the mineral series continues from the scheelite to powellite ends above a room temperature.

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Deep sea manganese nodules from the Central Pacific Basin are mainly composed of 10Å manganite and δ-MnO ₂ Two zones equivalent to the minerals are evidently distinguishable according to their optical properties. Microscopic and microprobe analyses revealed quite different chemical compositions and textnral characteristics of the two zones. These different feature of the two zones of nodules suggest the different conditions under which they were formed. Concentrations of 11 metal elements in the zones and inter-element relationships show that the 10Å manganite zone is a monomineralic oxide phase containing a large amount of manganese and minor amounts of useful metals, and that the δ-MnO ₂ zone which is apparently homogeneous under the microscope is a mixture of three or more different minerals. The chemical characteristics of the two zones can explain the variation of bulk composition of deep sea manganese nodules and inter-element relationships previously reported, suggesting that the bulk compositions are attributable to the mixing of the 10Å manganite and δ-MnO ₂ zones in various ratios. Characteristic morphology and surface structure of some types of nodules and their relationships to chemistry are also attribut able to the textural and chemical features of the above mentioned two phases.
Synthesis of hydrated manganese oxides was carried out in terms of the formation of manganese minerals in the ocean. The primary product which is an equivalent to δ-MnO ₂ was precipitated from Mn ²⁺ -bearing alkaline solution under oxigenated condition by air bubbling at one atmospheric pressure and room temperature. The primary product was converted to a l0Å manganite equivalent by contact with Ni ²⁺, Cu ²⁺+ or CO₂+ chloride solutions. This reaction caused the decrease of Ni ²⁺, Cu ²⁺ or CO₂+ concentrations and the increase of Na ⁺ concentration in the solution. The reaction also proceeded even in diluted solutions of nickel chloride and resulted in a complete removal of Ni ²⁺ from the solution. Reaction products were exclusively 10Å manganite equivalents and their chemical compositions were very similar to those of 10Å manganite in manganese nodules. The maximum value of(Cu+Ni+Co)/Mn ratio of 10Å manganite zones in manganese nodules is 0.16, and the Ni/Mn ratio of synthetic 10Å manganite ranges from 0.15 to 0.18 with the average of 0.167.

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Ore lead isotope data of the Kamioka and nearby lead-zinc mineralizations in the Hida metamorphic terrain are variable. Small but distinct isotopic variation is observed even in a single ore deposit. The ore lead in this area seems to have come from more than a single source of material.

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