Orthoericssonite from the Hijikuzu mine, Iwate Prefecture, Japan, (Ba_0.7Sr_0.3) (Mn²⁺_1.4Fe²⁺_0.6)(Fe³⁺_0.9Ti_0.1)Si₂O₇(O, OH)₂, is orthorhombic, space group Pnmn, with unit cell parameters a=20.230(5), b=6.979(2), c=5.392(2)Å and Z=4. The crystal structure has been determined based on three-dimensional Patterson and Fourier syntheses and refined to R=0.054 for 1626 independent reflections.
The structure contains composite sheets each built up of a pair of quasi-silicate sheets consisting of Si₂O₇ groups and square pyramids formed by oxygen atoms about Fe³⁺, intercalating between the pair a sheet of octahedra formed by oxygen atoms about Mn²⁺. The composite sheets are separated by (Ba, Sr) atoms. The orthoericssonite structure can be derived from a monoclinic subcell, which has dimensions a′=10.19, b′=6.979, c′=5.392Å, β 96°45′ and P2⁄m, after polysynthetically twinning them on {100}, with a glide reflection having the glide component of ^b⁄₂ as twin operation. If the subcells are juxtaposed on {100}, with a glide of ^b⁄₂, stepwise in one direction, the ericssonite cell is obtained. The relationship between orthoericssonite and ericssonite thus offers an example of cell twinning.
The minerals containing quasi-silicate sheets can be structurally classified in terms of different combinations of the stackings of various types of quasi-silicate sheets and intersheet cations or groups.

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Nagashimalite, Ba₄(V³⁺,Ti)₄[(O,OH)₂|Cl|Si₈B₂O₂₇], is orthorhombic, space group Pmmn, unit cell parameters: a=13.937(3), b=12.122(3), c=7.116(2)Å, Z=2. The strongest lines in the X-ray powder pattern are: 3.854(25) (221), 3.319(15) (112), 3.173(15) (202), 3.030(60) (040, 411), 3. 020(100) (420), 2.791(20) (041), 2.592(28) (501, 241), 1.785(15) (641), 1.287(15) (771). It is greenish black in colour, lustre submetallic to vitreous. Streak green. No cleavage. VHN (load 100 g) 606–681 kg/mm² (=6 (Mohs)). Specific gravity 4.08 (meas.), density 4.14 g/cm³(calc.). It is optically biaxial, positive, 2V=30°(obs.), r>v strong; refractive indices α=1.750(2), β=1.753(2), γ=1.780(5) ; optical orientation a=X, b=Z, c=Y; pleochroism strong, X=greenish yellow, Y=green, Z=greenish brown, absorption X<Y<Z. The mineral occurs as prismatic crystals and their aggregates in massive rhodonite ore from a bedded manganese ore deposit of the Mogurazawa mine, Gumma Prefecture, Japan.

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Nagashimalite, Ba₄(V³⁺_3.44Ti_0.56)B₂Si₈O₂₈Cl[(OH)_0.44O_0.56], a new mineral from the Mogurazawa mine, Gumma Prefecture, is orthorhombic, space group Pmmn, with unit cell parameters a=13.937(3), b=12.122(3), c=7.116(2)Å and Z=2.
The crystal structure is similar to that of taramellite after Mazzi and Rossi (1965), except for boron and chlorine. It basically consists of a novel borosilicate group [Si₈B₂O₂₇] which is built up of a pair of Si₄O₁₂ groups linked together, sharing corners, by a B₂O₇ group. These borosilicate groups are in the structure joined together by sharing of octahedra, parallel to b, formed by oxygen atoms about vanadium atoms. The crystallochemical formula is thus given as Ba₄(V³⁺,Ti)₄[(O, OH)₂|Cl|Si₈B₂O₂₇]. Mean interatomic distances are: V–O=2. 012(5), Si(1)–O=1.631(4), Si(2)–O=1.617(4), and B–O=1.479(5)Å. The Ba atoms are thirteen and eleven-coordinated with mean distances of Ba(1)^[13]–(O, OH)=3.094(6), Ba(2)^[11]–(O, Cl)=3.121(8), and Ba(3)^[11]–(O, Cl)=2.925(8)Å.
It appears that the reported taramellite structure would in fact contains boron atoms and belongs to the same borosilicate groups as nagashimalite.

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Bulky single crystals of hexagonal BaTiO₃ were grown by the flux method using KF and K₂CO₃ without quenching. The crystals of amber color have a hexagonal dipyramid-like habit belonging to the holohedral class D_6h–6⁄mmm with their lattice parameters a=5.722±0.002 and c=14.049±0.003 Å and with the space group P6₃⁄mmc. K₂CO₃ is very effective to grow the bulky BaTiO₃ single crystals.

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