Anandite, a new barium iron silicate from Wilagedera, North Western Province, Ceylon

Pattiaratchi, D. B.; Saari, Esko; Sahama, Th. G.

doi:10.1180/minmag.1967.036.277.01

Cited by 22 publications

(21 citation statements)

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“…If the Ba-for-K substitution exceeds 0.5 a.p.f.u., the mica is kinoshitalite (57 analyses) or oxykinoshitalite (2 analyses), an exotic, Ti-enriched mica known only from an olivine nephelinite (Kogarko et al, 2005). Ferrokinoshitalite (4 analyses) is a brittle mica with an octahedral sheet resembling that of annite (Guggenheim and Frimmel, 1999), whereas anandite (5 analyses, Pattiaratchi et al, 1967) has an additional condition, namely that IV Al be replaced by IV Fe 3+ and that S be incorporated instead of one (OH). In dioctahedral micas, a partial replacement of K by Ba results in the formation of ganterite (13 analyses, Hetherington et al, 2003;Ma and Rossman, 2006) or chernykhite (2 analyses), if VI V simultaneously substitutes for VI Al.…”

Section: Fig 10 Proportion Of Nh 4 Inmentioning

confidence: 99%

True and brittle micas: composition and solid-solution series

Tischendorf¹,

Förster²,

Gottesmann³

et al. 2007

Mineral. mag.

150

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Micas incorporate a wide variety of elements in their crystal structures. Elements occurring in significant concentrations in micas include: Si, IVAl, IVFe3+, B and Be in the tetrahedral sheet; Ti, VIAl, VIFe3+, Mn3+, Cr, V, Fe2+, Mn2+, Mg and Li in the octahedral sheet; K, Na, Rb, Cs, NH4, Ca and Ba in the interlayer; and O, OH, F, Cl and S as anions. Extensive substitutions within these groups of elements form compositionally varied micas as members of different solid-solution series. The most common true K micas (94% of almost 6750 mica analyses) belong to three dominant solid-solution series (phlogopite–annite, siderophyllite–polylithionite and muscovite–celadonite). Theirclassification parameters include: Mg/(Mg+Fetot) [=Mg#] formicas with VIR >2.5 a.p.f.u. and VIAl <0.5 a.p.f.u.; Fetot/(Fetot+Li) [=Fe#] formicas with VIR >2.5 a.p.f.u. and VIAl >0.5 a.p.f.u.; and VIAl/(VIAl+Fetot+Mg) [=Al#] formicas with VIR <2.5 a.p.f.u. The common true K micas plot predominantly within and between these series and have Mg6Li <0.3 a.p.f.u. Tainiolite is a mica with Mg6Li >0.7 a.p.f.u., or, fortr ansitional stages, 0.3–0.7 a.p.f.u. Some true K mica end-members, especially phlogopite, annite and muscovite, form binary solid solutions with non-K true micas and with brittle micas (6% of the micas studied). Graphical presentation of true K micas using the coordinates Mg minus Li (= mgli) and VIFetot+Mn+Ti minus VIAl (= feal) depends on theirclassification according to VIR and VIAl, complemented with the 50/50 rule.

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Section: Fig 10 Proportion Of Nh 4 Inmentioning

confidence: 99%

True and brittle micas: composition and solid-solution series

Tischendorf¹,

Förster²,

Gottesmann³

et al. 2007

Mineral. mag.

150

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“…The presence of tetrahedrally coordinated ferric iron has long been recognized in some layer silicates. Various synthetic phases, such as the iron mica of composition KFe2+3(Si3Fes+)O10(OH)2 described by Donnay et al (1964), rare phlogopites of composition (K0.gMn0.a)Mg3[Si3(Fe3+,Mn)O10(OH) 2 (Steinfink, 1962), and the rare, brittle mica anandite Copyright 9 1983, The Clay Minerals Society (Pattiaratchi et al, 1967) contain significant amounts of tetrahedrally coordinated Fe 3+. Inasmuch as Si and Fe z+ occur in a favorable tetrahedral ratio ideally near 1:1 and have radically different effective ionic radii in tetrahedral coordination, 0.26 A and 0.49 A (high spin), respectively (Shannon, 1976), the possibility of tetrahedral ordering should be investigated in cronstedtite.…”

Section: Introductionmentioning

confidence: 99%

Crystal Structure of Cronstedtite-2H₂

Geiger¹,

Henry

Bailey

et al. 1983

Clays and clay miner.

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The crystal structure of a magnesian cronstedtite-2H2 from P~l'bram, Czechoslovakia, was refined in space group C 1 to a residual of 5.4% with 1832 independent reflections. Tetrahedral ordering between Fe a+ and Si is judged to be complete on the basis of electron density maps, the first confirmation of such ordering in a layer silicate. Octahedral cations are disordered on the M sites. Mean T-O bond lengths do not confirm the tetrahedral ordering, perhaps due to tetrahedral distortion in order to relieve the extreme corrugation of the sheet that would arise from ordering of such different size cations.In the initial stages of refinement the structure of the crystal under study could not be described adequately on the basis of a single 2H2 polytype. The structure contains two kinds of 2Hz domains that appear shifted by b/3 relative to one another due to a mistake in the interlayer stacking sequence. This mistake of zero shift (the normal 2H~ polytype consists of alternating -b/3 and +b/3 shifts) affects only the tetrahedral sheets. It creates adjacent enantiomorphic domains of 2H z packets such that domains with small Si tetrahedra sit above larger FeZ+-rich tetrahedra and vice versa. This mechanism to relieve strain may indeed be the cause of the stacking mistakes. A third kind of domain contains regions in which the sense of tetrahedral rotation is reversed, giving rise to split basal oxygens on electron density maps. This multiple domain model best explains extra atomic positions observed on Fourier maps, lack of streaking of k ~ 3n reflections, and possible nonintegral "satellitic" reflections observed on Weissenberg films.

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“…All of these are so similar in crystallography, chemical composition, and mode of origin that only a single species name is justified (Forman et al, 1967). Bityite (Li,Be-rich), anandite (Ba,Fe-rich), and kinoshitalite (Ba,Mg-rich) appear to be other valid trioctahedral brittle mica species (Schaller et al, 1967;Pattiaratchi et al, 1967;Yoshii et al, 1973). Ephesite, described originally as a Li-Na brittle mica (Schaller et al, 1967), is described better as a true mica with a layer charge per formula unit of unity.…”

Section: Miscellaneousmentioning

confidence: 99%