Structure of homilite, Ca2.00(Fe0.90Mn0.03)B2.00Si2.00O9.86(OH)0.14

Miyawaki, Ritsuro; Nakai, Ikuo; Nagashima, Kōzō

doi:10.1107/s010827018500261x

Cited by 9 publications

(16 citation statements)

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“…The M site is commonly occupied by Fe 2þ as in gadolinites (e.g. Miyawaki et al, 1984;Demartin et al, 2001;Cámara et al, 2008) and homilite (Miyawaki et al, 1985), although other divalent cations with ionic radius close to Fe 2þ (Mg, Mn, Co, Ni, Cu and Zn À Ito & Hafner, 1974;Ni À Foit & Gibbs, 1975) can also enter the site. Nevertheless, the M site might also host large divalent cations like Ca in minasgeraisite-(Y), although the local strain requires relaxation and lowering of symmetry (Atencio, unpublished data).…”

Section: The M Sitementioning

confidence: 99%

“…Description: Homilite was first described by Paijkull (1876). Structure was solved by Miyawaki et al (1985) on the material from type locality. The composition of the described homilite is near end-member with only up to 0.07 apfu ' □ and 0.03 apfu Mn (Miyawaki et al, 1985).…”

Section: Appendixmentioning

confidence: 99%

“…Structure was solved by Miyawaki et al (1985) on the material from type locality. The composition of the described homilite is near end-member with only up to 0.07 apfu ' □ and 0.03 apfu Mn (Miyawaki et al, 1985). Homilite usually occurs in pegmatite bodies (Paijkull, 1876;Brögger, 1890).…”

Section: Appendixmentioning

confidence: 99%

“…Location of holotype: Muséum National d'Histoire Naturelle, Galerie Nationale de Minéralogie et de Géologie, Paris, France (catalogue # 78142), Naturhistoriske Riksmuseet, Sektionen för Mineralogi, Stockholm, Sweden (catalogue # 531010). Selected references: Paijkull (1876) and Miyawaki et al (1985).…”

Section: Appendixunclassified

“…Foit et al, 1973) and choice 3, P2 1 /a (e.g. Miyawaki et al, 1984Miyawaki et al, , 1985. For an internally consistent description of all members of the supergroup, we use here only P2 1 /c.…”

Section: Introductionmentioning

confidence: 99%

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Nomenclature of the gadolinite supergroup

Bačík¹,

Miyawaki²,

Atencio³

et al. 2017

ejm

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The newly defined gadolinite supergroup approved by the IMA CNMNC (vote 16-A) includes mineral species that have the general chemical formula A 2 MQ 2 T 2 O 8 ' 2 and belong to silicates, phosphates and arsenates. Each site is occupied by: A À Ca, REE (Y and lanthanoids), actinoids, Pb, Mn 2þ , Bi; M À Fe, □ (vacancy), Mg, Mn, Zn, Cu, Al; Q À B, Be, Li; T À Si, P, As, B, Be, S; and ' À O, OH, F. The classification of the gadolinite supergroup is based on the occupancy of A, M, Q, T and ' sites and application of the dominant-valency and dominant-constituent rules. The gadolinite supergroup is divided into two groups defined by prevailing charge occupancy at the T site À Si 4þ in gadolinite group and P 5þ or As 5þ in herderite group. The gadolinite group is divided into the gadolinite and datolite subgroups. The A site is dominantly occupied by divalent cations in the datolite subgroup and by trivalent cations in the gadolinite subgroup. Accordingly, the Q site is dominantly occupied by B 3þ in the datolite subgroup and by Be 2þ in the gadolinite subgroup. The herderite group is divided into two subgroups. The herderite subgroup is defined by the dominant divalent cation (usually Ca 2þ ) in the A site and Be 2þ in the Q site, while the M site is vacant. The drugmanite subgroup is defined by the dominance of divalent cations (usually Pb 2þ ) in the A site, vacancy in the Q site and the occupation of the M site. Moreover, "bakerite" is discredited as mineral species because it does not meet the conditions of the dominant-constituent rule.

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Section: The M Sitementioning

confidence: 99%

Section: Appendixmentioning

confidence: 99%

Section: Appendixmentioning

confidence: 99%

Section: Appendixunclassified

Section: Introductionmentioning

confidence: 99%

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Nomenclature of the gadolinite supergroup

Bačík¹,

Miyawaki²,

Atencio³

et al. 2017

ejm

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Polymorphs of the Gadolinite‐Type Borates ZrB₂O₅ and HfB₂O₅ Under Extreme Pressure

Pakhomova

Fuchs

Dubrovinsky

et al. 2021

Chemistry A European J

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Based on the results from previous high‐pressure experiments on the gadolinite‐type mineral datolite, CaBSiO4(OH), the behavior of the isostructural borates β‐HfB2O5 and β‐ZrB2O5 have been studied by synchrotron‐based in situ high‐pressure single‐crystal X‐ray diffraction experiments. On compression to 120 GPa, both borate layer‐structures are preserved. Additionally, at ≈114 GPa, the formation of a second phase can be observed in both compounds. The new high‐pressure modification γ‐ZrB2O5 features a rearrangement of the corner‐sharing BO4 tetrahedra, while still maintaining the four‐ and eight‐membered rings. The new phase γ‐HfB2O5 contains ten‐membered rings including the rare structural motif of edge‐sharing BO4 tetrahedra with exceptionally short B−O and B⋅⋅⋅B distances. For both structures, unusually high coordination numbers are found for the transition metal cations, with ninefold coordinated Hf4+, and tenfold coordinated Zr4+, respectively. These findings remarkably show the potential of cold compression as a low‐energy pathway to discover metastable structures that exhibit new coordinations and structural motifs.

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