The composition and structure of jeanbandyite and natanite

Betterton, J.O.; Green, D. I.; Jewson, C.; Spratt, John; Tandy, Peter C.

doi:10.1180/002646198547945

Cited by 8 publications

(9 citation statements)

References 8 publications

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“…and B' sites of the two jeanbandyite crystals are in good agreement with those calculated from their average empirical formulas reported by Betterton et al (1998) and Kampf (1982), when these formulas are correctly formulated as described above.…”

Section: Pn3supporting

confidence: 87%

“…Jeanbandyite was re-examined by Betterton et al (1998) from Hingston Down Quarry, Cornwall (UK), who noted that the empirical formula of Kampf (1982) did not consider the presence of divalent iron and was not charge-balanced. They proposed a revised charge-balanced average empirical formula (Fe 3þ 0:46 Fe 2þ 0:24 Mn 2þ 0:14 Mg 0.03 ) (Sn 4þ 0:90 Si 0.05 )(OH) 6 .…”

Section: •••O-h•••o-hmentioning

confidence: 99%

“…Jeanbandyite was re-examined by Betterton et al (1998) Si 0.05 ) (OH) 6 . However, this revised formula also implies 13 % vacancies at B sites.…”

Section: Introductionmentioning

confidence: 99%

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Stoichiometric partially-protonated states in hydroxide perovskites: the jeanbandyite enigma revisited

Welch

Kampf

2017

Mineral. mag.

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The original description of the hydroxide perovskite jeanbandyite gives a formula (Fe 3+ 1-x ,  x )(Sn 1-y ,  y )(OH) 6 ( = vacancy), which implies the possibility of stoichiometric vacancies at B and B' sites. The validity of this formula has been questioned subsequently.Furthermore, jeanbandyite has metrically cubic unit cell, but it is optically uniaxial. It is clear that a structure determination is needed to clarify the nature of this enigmatic mineral.Previous studies could not find crystals of sufficient quality for structure determination using X-ray diffractometers available at the time. Crystals of jeanbandyite from Hingston Downs, Cornwall, UK and the type locality Llallagua, Bolivia, have been found that are of a quality that allows structure refinement by single-crystal X-ray diffraction. Structural data for crystals from each locality are presented that clarify the nature of jeanbandyite and raise some interesting questions concerning the significance of partially deprotonated states in perovskite-type structures. The structures of both jeanbandyite crystals are cubic with space group Pn3 and unit-cell parameters a = 7.658(2) Å (Llallagua) and 7.6427(2) Å (Hingston). (1-x) Sn(OH) (6-x) O x for 1  x > 0.5, with an ideal end-member formula Fe 3+ Sn(OH) 5 O.As such, jeanbandyite corresponds to oxidised natanite with partially deprotonated oxygen sites. This stoichiometry cannot be represented in space group Pn3 for the observed unit cell as it implies more than one non-equivalent oxygen atom. Consequently, it is inferred that there is no long-range ordering of deprotonated oxygen sites. It is, however, conceivable that the uniaxial optical character of jeanbandyite is linked to the local short-range order of deprotonated domains.

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Section: Pn3supporting

confidence: 87%

Section: •••O-h•••o-hmentioning

confidence: 99%

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Stoichiometric partially-protonated states in hydroxide perovskites: the jeanbandyite enigma revisited

Welch

Kampf

2017

Mineral. mag.

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“…Kampf (1982) (OH) 6 , in which vacancies are a potentially significant component. Jeanbandyite was re-examined by Betterton et al (1998) from Hingston Down Quarry, Cornwall (UK), who noted that the empirical formula of Kampf (1982) did not consider the presence of divalent cations and was not charge-balanced. They proposed a revised empirical formula (Fe 3þ 0:46 Fe 2þ 0:24 Mn 2þ 0:14 Mg 0.03 )(Sn 4þ 0:90 Si 0.05 )(OH) 6 , which is charge-balanced.…”

Section: Double Hydroxide Perovskitesmentioning

confidence: 99%

“…In view of the uncertainties in the formula of jeanbandyite and the absence of a structure determination, Welch and Kampf (2017) re-examined samples from Llallagua (Kampf, 1982) and Hingston Down (Betterton et al, 1998), and determined the structures of crystals from both localities. All crystals are cubic with space group Pn 3 and have fully-occupied B-and B′-sites (Fe and Sn, respectively).…”

Section: Double Hydroxide Perovskitesmentioning

confidence: 99%

Nomenclature of the perovskite supergroup: A hierarchical system of classification based on crystal structure and composition

2017

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On the basis of extensive studies of synthetic perovskite-structured compounds it is possible to derive a hierarchy of hettotype structures which are derivatives of the arisotypic cubic perovskite structure (ABX3), exemplified by SrTiO3 (tausonite) or KMgF3 (parascandolaite) by: (1) tilting and distortion of the BX6 octahedra; (2) ordering of A- and B-site cations; (3) formation of A-, B- or X-site vacancies. This hierarchical scheme can be applied to some naturally-occurring oxides, fluorides,hydroxides, chlorides, arsenides, intermetallic compounds and silicates which adopt such derivative crystal structures. Application of this hierarchical scheme to naturally-occurring minerals results in the recognition of a perovskite supergroup which is divided into stoichiometric and non-stoichiometricperovskite groups, with both groups further divided into single ABX3 or double A2BB'X6 perovskites. Subgroups, and potential subgroups, of stoichiometric perovskites include: (1) silicate single perovskites of the bridgmanite subgroup;(2) oxide single perovskites of the perovskite subgroup (tausonite, perovskite, loparite, lueshite, isolueshite, lakargiite, megawite); (3) oxide single perovskites of the macedonite subgroup which exhibit second order Jahn-Teller distortions (macedonite, barioperovskite); (4) fluoride singleperovskites of the neighborite subgroup (neighborite, parascandolaite); (5) chloride single perovskites of the chlorocalcite subgroup; (6) B-site cation ordered double fluoride perovskites of the cryolite subgroup (cryolite, elpasolite, simmonsite); (7) B-site cation orderedoxide double perovskites of the vapnikite subgroup [vapnikite, (?) latrappite]. Non-stoichiometric perovskites include: (1) A-site vacant double hydroxides, or hydroxide perovskites, belonging to the söhngeite, schoenfliesite and stottite subgroups; (2) Anion-deficient perovskitesof the brownmillerite subgroup (srebrodolskite, shulamitite); (3) A-site vacant quadruple perovskites (skutterudite subgroup); (4) B-site vacant single perovskites of the oskarssonite subgroup [oskarssonite]; (5) B-site vacant inverse single perovskites of the coheniteand auricupride subgroups; (6) B-site vacant double perovskites of the diaboleite subgroup; (7) anion-deficient partly-inverse B-site quadruple perovskites of the hematophanite subgroup.

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Ottensite, brizziite and mopungite from Pereta mine (Tuscany, Italy): new occurrences and crystal structure refinement of mopungite

et al. 2015

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The composition and structure of jeanbandyite and natanite

Cited by 8 publications

References 8 publications

Stoichiometric partially-protonated states in hydroxide perovskites: the jeanbandyite enigma revisited

Stoichiometric partially-protonated states in hydroxide perovskites: the jeanbandyite enigma revisited

Nomenclature of the perovskite supergroup: A hierarchical system of classification based on crystal structure and composition

Ottensite, brizziite and mopungite from Pereta mine (Tuscany, Italy): new occurrences and crystal structure refinement of mopungite

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