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  • 1980-1984  (3)
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  • 1
    Electronic Resource
    Electronic Resource
    Schumacherit, ein neues Wismutmineral von Schneeberg in Sachsen (1983)
    Springer
    Mineralogy and petrology 31 (1983), S. 165-173 
    Details
    ISSN: 1438-1168
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Summary Schumacherite occurs in association with pucherite in crusts on quartz-bearing vein specimens from Schneeberg in Saxony. The mineral forms minute triclinic crystals which frequently are tabular parallel to (010). No cleavage, fracture conchoidal, hardness about 3,D x =6.90 g/cm3, colour yellow, luster more or less adamantine. Indices of refraction variable,n γ(max.)=2,42, biaxial with very large 2V, probably positive. Unit cell dimensions:a 0=10.05(3),b 0=7.46(3),c 0=6.90(3) Å, α=87.7(3)0, β=115.3(3)0, γ=111.5(3)0,Z=2, space group $$P\bar 1$$ . Strongest lines of the powder pattern: 4.57 (6) 110, $$\bar 201$$ ; 3.28 (10) $$\bar 221$$ , $$\bar 202$$ ; 3.19 (8) $$0\bar 21$$ , 111; 3.09 (8) 002, 210, $$2\bar 11$$ , $$\bar 112$$ ; 1.976 (5) $$3\bar 31$$ , $$0\bar 32$$ , $$\bar 512$$ , $$\bar 430$$ , $$\bar 4\bar 12$$ . Analysis: Bi2O3 79.0, V2O5 10.9, As2O5 5.8, P2O5 3.6, H2O 1.0% (calc.), sum 100.3%. This yields the formula Bi3.03(V1.07As0.45P0.45)1.97H1.00O9.97 or idealized Bi3O(OH)(VO4)2. Schumacherite is the vanadium analogue of preisingerite. When heated to higher temperatures the mineral is subject to a structural transformation which is evidenced by a marked change in the powder pattern.
    Notes: Zusammenfassung Schumacherit kommt in Vergesellschaftung mit Pucherit krustenförmig auf quarzreichen Gangstufen von Schneeberg in Sachsen vor. Das Mineral bildet kleine, zum Teil nach (010) tafelige Kristalle von trikliner Symmetrie. Keine Spaltbarkeit, Bruch muschelig, Härte ca. 3,D x =6,90 g/cm3, Farbe gelb, Glanz mehr oder minder diamantartig; Brechungsindizes variabel,n γ(max.)=2,42, zweiachsig mit sehr großem 2V, wahrscheinlich positiv. Gitterkonstanten:a 0=10,05(3),b 0=7,46(3),c 0=6,90(3) Å, α=87,7(3)0, β=115,3(3)0, γ=111,5(3)0,Z=2, Raumgruppe $$P\bar 1$$ . Stärkste Linien des Pulverdiagramms: 4,57 (6) 110, $$\bar 201$$ ; 3,28 (10) $$\bar 221$$ , $$\bar 202$$ ; 3,19 (8) $$0\bar 21$$ , 111; 3,09 (8) 002, 210, $$2\bar 11$$ , $$\bar 112$$ ; 1,976 (5) $$3\bar 31$$ , $$0\bar 32$$ , $$\bar 512$$ , $$\bar 430$$ , $$\bar 4\bar 12$$ . Analysenergebnis: Bi2O3 79,0, V2O5 10,9, As2O5 5,8, P2O5 3,6, H2O 1,0% (ber.), Summe 100,3%. Dies führt zur Formel Bi3,03(V1,07As0,45P0,45)1,97H1,00O9,97 oder idealisiert Bi3O(OH) (VO4)2. Schumacherit ist das dem Preisingerit entsprechende Vanadatmineral. Beim Erhitzen auf höhere Temperaturen kommt es zu einem Umwandlungsvorgang, der sich in einer stärkeren Veränderung des Pulverdiagramms äußert.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01084768
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  • 2
    Electronic Resource
    Electronic Resource
    Osumilith in der Eifel und die Verwendung dieses Minerals als petrogenetischer Indikator (1983)
    Springer
    Mineralogy and petrology 31 (1983), S. 215-234 
    Details
    ISSN: 1438-1168
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Summary Osumilites from 5 quaternary volcanoes of the Eifel, West Germany, were investigated. They occur within contact-metamorphosed xenoliths, mostly in vesicles as deposits from the gas phase, in one case as porphyroblasts within the rock formed at depth. 6 out of 7 osumilites analyzed show M=Mg/(Mg+Fetot+Mn)-values between 0.66 and 0.86, the porphyroblastic osumilite being the richest in Mg. One osumilite, which has optically negative character and unusually small cell edges, shows M=0.17 and is the most iron-rich osumilite known thus far; in addition, it has the lowest alkali content ever reported. Alkali deficiencies of osumilites seem to be predominantly due to the substitution □+Fe3+→(K,Na)++Fe2+. A histogram of all M-values of osumilites taken from the literature shows practically a complete series of Mg−Fe solid solution in which the deep-seated osumilites formed at high pressure are invariably very Mg-rich magnesio-osumilites, while all ferro-osumilites are of near-surface origin under low pressures. This indicates that the PT-stability range of magnesio-osumilite is considerably larger than that of ferro-osumilite, similarly as for the structurally related series of Mg−Fe-cordierites. Alkali deficiencies in osumilites are not always linked to high total iron contents; they are also observed in Mg-enriched osumilites though never in those formed at high pressures. Probably the alkali-deficiencies are indicators of relatively high oxygen fugacities as they are typical for the Eifel volcanic environment and evidenced by accompanying minerals like hematite, pseudobrookite, and acmitic pyroxenes.
    Notes: Zusammenfassung Osumilithe aus 5 quartären Vulkanen der Eifel wurden untersucht. Sie kommen in kontaktmetamorph veränderten Nebengesteinseinschlüssen (Xenolithen) vor, und zwar meist in Drusenräumen als Abscheidung aus der Gasphase, in einem Fall auch als porphyroblastischer, intratellurisch gebildeter Gefügebestandteil des festen Gesteins. 6 von 7 analysierten Osumilithen zeigen M=Mg/(Mg+Fetot+Mn)-Werte zwischen 0,66 und 0,86, wobei der intratellurische Osumilith der Mg-reichste ist. Ein optisch negativer Osumilith mit kleineren Gitterkonstanten und dem M-Wert von 0,17 ist das bisher Fe-reichste Glied der Reihe, das auch außerdem den niedrigsten bisher bekannten Alkaligehalt aufweist. Alkali-Defizite in Osumilithen scheinen vorwiegend auf die Substitution □+Fe3+→(K,Na)++Fe2+ zurückzugehen. Ein Histogramm aller M-Werte von Osumilithen aus der Literatur zeigt praktisch eine durchgehende Mg−Fe-Mischreihe, in der intratellurische Osumilithe, besonders die bei hohem Druck gebildeten, immer sehr Mg-reiche Magnesio-Osumilithe sind, während alle Ferro-Osumilithe oberflächennahe Bildungen unter niedrigem Druck darstellen. Hieraus ist zu folgern, daß das PT-Stabilitätsfeld von Magnesio-Osumilith beträchtlich größer ist als dasjenige von Ferro-Osumilith, ähnlich wie dei der strukturell ähnlichen Reihe der Mg−Fe-Cordierite. Alkali-Defizite im Osumilith sind keinesfalls immer mit hohem Fetot-Gehalt verknüpft; sie kommen auch in Mg-reicheren Gliedern der Osumilithreihe vor, allerdings nie in intratellurisch, unter hohem Druck gebildetem Material. Wahrscheinlich sind die Alkali-Defizite Indikatoren für relativ hohe Sauerstoff-Fugazitäten, wie sie für das vulkanische Milieu der Eifel typisch und durch Begleitminerale wie Hämatit, Pseudobrookit und akmitische Pyroxene auch erwiesen sind.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01081370
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  • 3
    Electronic Resource
    Electronic Resource
    Eifelite, KNa3Mg4Si12O30, a new mineral of the osumilite group with octahedral sodium (1983)
    Springer
    Contributions to mineralogy and petrology 82 (1983), S. 252-258 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Eifelite of variable composition is uniaxial positive withn 0 near 1.543 andn e near 1.544, a between 10.14 and 10.15 Å, andc about 14.22 Å, space groupP 6/m 2/c 2/c. There is a complete series of solid solution between the eifelite end member KNa3Mg4Si12O30 and roedderite, KNaMg5Si12O30, following the 2 Na⇌Mg substitution. Both eifelite and roedderite have milarite-type structures, but Na is always in six-coordinated sites: In roedderite Na occupies solely a newly defined B′[6]-position which is slightly displaced alongc from the ideal B[9]-position lying on the (001/2)-mirror plane in K2Mg5Si12O30. In eifelite Na is located both inB′[6] and in theA [6]-positions, where it partially replaces Mg. Eifelite has the highest cation occupancy of all osumilite group minerals known thus far. Both eifelite and roedderite occur in vesicles of contact metamorphosed basement xenoliths ejected with the leucite tephrite lava of the Quaternary Bellerberg volcano in the Eifel, West Germany. They are considered to be precipitates from highly alkaline, MgSi-rich, but Al-deficient gas phases that originated through interaction of gaseous igneous differentiates with the xenoliths.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01166619
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