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Open AccessArticle

Rippite, K2(Nb,Ti)2(Si4O12)O(O,F), a New K-Nb-Cyclosilicate from Chuktukon Carbonatite Massif, Chadobets Upland, Krasnoyarsk Territory, Russia

1
V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the RAS, 3 Acad. Koptyuga pr., 630090 Novosibirsk, Russia
2
ExtraTerra Consortium, Institute of Physics and Technology, Ural Federal University, 19 Mira str., 620002 Ekaterinburg, Russia
3
Department of Geology and Geophysics, Novosibirsk State University, 1 Pirogov str., 630090 Novosibirsk, Russia
4
Geological Institute, Siberian Branch of the RAS, 6a Sakhyanova str., 670047 Ulan-Ude, Russia
5
South Urals Federal Research Center of Mineralogy and Geoecology, Uralian Branch of the RAS, 456317 Miass, Russia
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Faculty of Geology, National Research South Ural State University, Miass Branch, 20 8-July str., Bldg. 10, 456304 Miass, Russia
*
Author to whom correspondence should be addressed.
Minerals 2020, 10(12), 1102; https://doi.org/10.3390/min10121102
Received: 9 November 2020 / Revised: 3 December 2020 / Accepted: 3 December 2020 / Published: 8 December 2020
(This article belongs to the Collection New Minerals)
Rippite K2(Nb,Ti)2(Si4O12)(O,F)2, a new K-Nb-cyclosilicate, has been discovered in calciocarbonatites from the Chuktukon massif (Chadobets upland, SW Siberian Platform, Krasnoyarsk Territory, Russia). It was found in a primary mineral assemblage, which also includes calcite, fluorcalciopyrochlore, tainiolite, fluorapatite, fluorite, Nb-rich rutile, olekminskite, K-feldspar, Fe-Mn–dolomite and quartz. Goethite, francolite (Sr-rich carbonate–fluorapatite) and psilomelane (romanèchite ± hollandite) aggregates as well as barite, monazite-(Ce), parisite-(Ce), synchysite-(Ce) and Sr-Ba-Pb-rich keno-/hydropyrochlore are related to a stage of metasomatic (hydrothermal) alteration of carbonatites. The calcite–dolomite coexistence assumes crystallization temperature near 837 °C for the primary carbonatite paragenesis. Rippite is tetragonal: P4bm, a = 8.73885(16), c = 8.1277(2) Å, V = 620.69(2) Å3, Z = 2. It is closely identical in the structure and cell parameters to synthetic K2Nb2(Si4O12)O2 (or KNbSi2O7). Similar to synthetic phase, the mineral has nonlinear properties. Some optical and physical properties for rippite are: colorless; Mohs’ hardness—4–5; cleavage—(001) very perfect, (100) perfect to distinct; density (meas.)—3.17(2) g/cm3; density (calc.)—3.198 g/cm3; optically uniaxial (+); ω = 1.737-1.739; ε = 1.747 (589 nm). The empirical formula of the holotype rippite (mean of 120 analyses) is K2(Nb1.90Ti0.09Zr0.01)[Si4O12](O1.78OH0.12F0.10). Majority of rippite prismatic crystals are weakly zoned and show Ti-poor composition K2(Nb1.93Ti0.05Zr0.02)[Si4O12](O1.93F0.07). Raman and IR spectroscopy, and SIMS data indicate very low H2O content (0.09–0.23 wt %). Some grains may contain an outermost zone, which is enriched in Ti (+Zr) and F, up to K2(Nb1.67Ti0.32Zr0.01)[Si4O12](O1.67F0.33). It strongly suggests the incorporation of (Ti,Zr) and F in the structure of rippite via the isomorphism Nb5+ + O2− → (Ti,Zr)4+ + F1−. The content of a hypothetical end-member K2Ti2[Si4O12]F2 may be up to 17 mol. %. Rippite represents a new structural type among [Si4O12]-cyclosilicates because of specific type of connection of the octahedral chains and [Si4O12]8− rings. In structural and chemical aspects it seems to be in close with the labuntsovite-supergroup minerals, namely with vuoriyarvite-(K), K2(Nb,Ti)2(Si4O12)(O,OH)2∙4H2O. View Full-Text
Keywords: rippite; new mineral; K-Nb-cyclosilicate; synthetic K2Nb2(Si4O12)O2; calciocarbonatite; Chuktukon massif; Chadobets upland; Krasnoyarsk Territory rippite; new mineral; K-Nb-cyclosilicate; synthetic K2Nb2(Si4O12)O2; calciocarbonatite; Chuktukon massif; Chadobets upland; Krasnoyarsk Territory
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MDPI and ACS Style

Sharygin, V.V.; Doroshkevich, A.G.; Seryotkin, Y.V.; Karmanov, N.S.; Belogub, E.V.; Moroz, T.N.; Nigmatulina, E.N.; Yelisseyev, A.P.; Vedenyapin, V.N.; Kupriyanov, I.N. Rippite, K2(Nb,Ti)2(Si4O12)O(O,F), a New K-Nb-Cyclosilicate from Chuktukon Carbonatite Massif, Chadobets Upland, Krasnoyarsk Territory, Russia. Minerals 2020, 10, 1102. https://doi.org/10.3390/min10121102

AMA Style

Sharygin VV, Doroshkevich AG, Seryotkin YV, Karmanov NS, Belogub EV, Moroz TN, Nigmatulina EN, Yelisseyev AP, Vedenyapin VN, Kupriyanov IN. Rippite, K2(Nb,Ti)2(Si4O12)O(O,F), a New K-Nb-Cyclosilicate from Chuktukon Carbonatite Massif, Chadobets Upland, Krasnoyarsk Territory, Russia. Minerals. 2020; 10(12):1102. https://doi.org/10.3390/min10121102

Chicago/Turabian Style

Sharygin, Victor V.; Doroshkevich, Anna G.; Seryotkin, Yurii V.; Karmanov, Nikolai S.; Belogub, Elena V.; Moroz, Tatyana N.; Nigmatulina, Elena N.; Yelisseyev, Alexander P.; Vedenyapin, Vitalii N.; Kupriyanov, Igor N. 2020. "Rippite, K2(Nb,Ti)2(Si4O12)O(O,F), a New K-Nb-Cyclosilicate from Chuktukon Carbonatite Massif, Chadobets Upland, Krasnoyarsk Territory, Russia" Minerals 10, no. 12: 1102. https://doi.org/10.3390/min10121102

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