Stannoidite was found in copper-tin-sulphide ores from xenothermal ore deposits of the four mines mentioned in the title. The mineral assemblages include chalcopyrite, mawsonite, bornite, sphalerite, galena, tennantite-tetrahedrite, cassiterite, and quartz as the common associates. Electron microprobe analyses verified the ideal formula Cu₅(Fe, Zn)₂SnS₈ with minor substi-tution for of copper by silver, and possible deficiency of sulphur leading to Cu₅(Fe, Zn)₂SnS₇. The occurrence of this mineral is rather common in copper-tin sulphide ores from Japanese xenothermal ore deposits.

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A new choice of unit layer proposed by Sadanaga & Takeda (1968) has been found useful for explaining the two characteristic features of the X-ray diffraction pattern of the mica, namely, the periodic intensity distribution and the partial enhancement of symmetry. The recognition of the fact that the symmetry of the new unit layers is higher than that of the crystal, played an important role in the derivation of intensity distribution functions.
By the introduction of four kinds of layer with either trigonal or hexagonal symmetry and designated D, D^*, T and T^*, the layer sequence of any mica polytype can be described by stacking of these layers in parallel orientation and with mutual staggers of 1/3·a₁, 1/3·a₂ and 1/3·a₃. With the aid of these new unit layers, it is proposed a new symbol to describe the stacking sequence of mica, together with a convention of axial settings to specify the symbol uniquely.

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The crystal structure of manganpyrosmalite has been determined. There are two chemical units of (Mn, Fe)₈Si₆O₁₅(OH, Cl)₁₀ in the unit cell of symmetry P 3 m 1 with a=13.42, c=7.159Å. The reciprocal lattice constructed from Weissenberg photographs revealed a marked substructure corresponding to the pyrochroite layer, suggesting that the structure contains the same type of layers. The structure analysis was therefore initiated with this assumption in mind, and a complement structure consisting of Si and O was determined by a partial Patterson synthesis. The structure thus determined revealed that a silicate sheet of a new type is contained, which is composed of 12-, 6- and 4-membered rings of SiO₄ tetrahedra with the ratio of 1:2:3, and the whole structure is built up of layers composite of a pyrochroite-like Mn octahedral sheet and a silicate sheet. Since this structure is the first example of Mn sheet silicates which, owing to the large size of Mn ions, inevitably exhibit considerable misfits between octahedral- and tetrahedral sheets, some details of deformations of these sheets are described.
The structures polytypic of this crystal and having three-fold axes are derived and possible polytypic relations between manganpyrosmalite-pyros-malite and schallerite-friedelite are discussed.

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