The relationship of the cell volume to the composition of humite solid solution, xMg(OH)₂·(1−x)MgF₂·nMg₂SiO₄ (0≤x≤1 and n=1, 2, 3 and 4) was formulated on the basis of the following model: The crystal of the humites is composed of small elastic blocks consisting of end member units, which have the different volume in the pure end members. Each block is constrained to have the same volume in the solid solution, and the strain energy is then stored in each block. The minimization criterion of the total strain energy is introduced to determine the equilibrium cell volume of the solid solution. The calculated cell volumes on this model agree with the observed values up to four figures for all the data available. Application of the present solid solution model is extended to cover the cation substitution in the humites and also to the solid solutions of alkali halide.

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Hexagonal ZrS₂(2H-type) and rhombohedral NbS₂(3R-type) single crystals were grown by the transport reactions between the constituent elements and an iodine carrier. The growing situation of ZrS₂ crystals (max. 10×10×2 mm³) in the ampoule changed from the hotter zone to the cooler zone with the increase of the iodine concentration, whereas NbS₂ crystals (max. 3×3×0.5 mm³) were usually in the cooler zone.
Although the {0001} surfaces of ZrS₂ crystals are very smooth, those of NbS₂ crystals exhibit vicinal faces which are characterized by the concentric arrangement of dislocations. Those vicinal surfaces disappeared in crystals grown under the conditions of lower supersaturations or higher temperatures with the same ΔT than the transport reactions from 950°C to 850°C.

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Crystals of xonotlite from Heguri, Chiba Prefecture, Japan, which exhibit relatively sharp k odd reflections have been found to be a triclinic variant having dimensions; a 8.712(2)Å, b 7.363(2)Å, c 14.023(4)Å, α=89.99(2)°, β=90.36(2)°, γ=102.18(2)°, and space group A-1; Z=2[Ca₆Si₆O₁₇(OH)₂]. The average structure which was determined using only even order reflections in k is similar to the reported average structure. Crystal-chemical consideration permitted to deconvolute the average structure to give the atomic arrangements for the true A-1 structure which has been refined to R=4.0% for observed reflections including odd order reflections in k. The structure consists of Si₆O₁₇ double chains, each consisting of a pair of Si₃O₉ chains of the wollastonite type and sheets of polyhedra about Ca’s. The structural scheme built up of these silicate chains and polyhedral sheets is similar to that of wollastonite though two of the three independent Ca atoms per cell are in trigonal prisms formed by oxygen atoms. Occupancy refinement of Ca appears to show that slight deficiency in Ca occurs only one of the three independent Ca sites.
The xonotlite polytypism can be discussed based on a monoclinic subcell, a_p 8.516Å, b_p 7.363Å, c_p 7.012Å, β_p=90.37°, underlying the A-1 structure. The polytypism may occur, unlike commonly known polytypism, in two directions, c and a: the monoclinic cell may be juxtaposed on (001) either in a continuous position or with a glide b⁄2 and on (100) with a glide b⁄4 (or −b⁄A).

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