The crystal structure of borax, Na₂B₄O₇•10H₂O, has been worked out by means of the sign relationships of structure factors and by the triple Fourier series method. The unit cell has the dimensions of a₀=11.858Å, b₀=10.674Å, c₀=12.197Å and β=106°41′, and the space group is C⁶_2h. There are four chemical units of composition, Na₂B₄O₇•10H₂O in the unit cell. The coordinates of atoms were refined first by double Fourier series and the final triple Fourier series were carried out with 1763 terms. The standard deviations of coordinates finally obtained are 0.004Å for sodium atoms, 0.02Å for boron atoms and 0.02Å for oxygen atoms. Hydrogen atoms have been located from the consideration on the electrostatic valencies directed to the oxygen atoms and the interatomic distances between oxygen atoms.
The structure of borax is composed of chains of regular octahedra formed by water molecules around Na, running parallel to the c-axis. These chains build up a sheet holding isolated groups of B₄O₅(OH)₄ in between them through hydrogen bonds. These sheets are parallel to (100) and held together mainly by hydrogen bonds. The structure formula of borax may best be represented with the expression B₄O₅(OH)₄•Na₂8H₂O.

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The crystal structure of vonsenite (iron-rich ludwigite) was determined by two dimensional fourier synthesis. The unit cell has the dimensions, a₀=9.73Å, b₀=12.35Å, c₀=3.05Å. The space group is Pbam. The structure is essentially the same as the structure of ludwigite obtained by earlier study. However, the present work was based upon much more accurate intensity data, so that the results provide a knowledge of the interatomic distances in detail.

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The chemical compositions of lithium micas in a pegmatite at Minagi, Okayama Prefecture, were studied. This pegmatite consists of five zones; (1) border zone, (2) biotite zone, (3) muscovite zone, (4) zinnwaldite zone and (4) lepidolite zone, arranged inwards successively. Each zone is characterized by their mineral assemblage, especially by the varieties of mica comprised in it.
It appears that iron and magnesium fit better into the mica structure than does lithium, and in the earlier stage the greater part of these elements are removed from the pegmatite solution forming biotite crystals. In the last stage of the cooling history of this pegmatite, the residual solution in which lithium had been gradually concentrated replaced the pre-existing feldspar, producing the lithium micas and secondary greenish violet hydrous alumina minerals. In the later stage, hydrothermal replacement is very remarkable and this is one of the distinctive characteristics of the lithium mica bearing pegmatite.

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It is concluded that the principal axes of absorption ellipsoid of heikolite are as follows: X nearly ⊥ (100), Y ?? [010] and Z nearly ?? [001]. The orientations of X and Z do not coincide with the principal axes of the indicatrix.

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