Kampelite, Ba3Mg1.5Sc4(PO4)6(OH)3·4H2O, a new very complex Ba-Sc phosphate mineral from the Kovdor phoscorite-carbonatite complex (Kola Peninsula, Russia)
“…One part of the PSM is formed in situ as rims around baddeleyite grains, and the other part is crystallized as individual crystals in carbonatites that act as a geochemical barrier for Nb(OH) 3 F 2 , Ta(OH) 3 F 3 + and other HFSE complexes [46,47]. Besides zirconolite-laachite, the typical PSM associated minerals in carbonate-rich rocks include Sc-phosphates juonniite and kampelite [27,48] Since Sc-Nb-rich baddeleyite and U-Ta-rich PSM of the ore-pipe axial zone contain most of the Kovdor's Nb, Ta, U, as well as a major part of Sc, this "Anomalous" zone can be regarded as a complex rare-metal deposit [6][7][8]. Prevailing close intergrowths of Sc-rich baddeleyite and U-rich kenopyrochlore significantly complicate the production of a high-quality baddeleyite concentrate.…”
The pyrochlore supergroup minerals (PSM) are typical secondary phases that replace (with zirconolite-laachite) earlier Sc-Nb-rich baddeleyite under the influence of F-bearing hydrothermal solutions, and form individual well-shaped crystals in surrounding carbonatites. Like primary Sc-Nb-rich baddeleyite, the PSM are concentrated in the axial carbonate-rich zone of the phoscorite-carbonatite complex, so their content, grain size and chemical diversity increase from the pipe margins to axis. There are 12 members of the PSM in the phoscorite-carbonatite complex. Fluorine-and oxygen-dominant phases are spread in host silicate rocks and marginal carbonate-poor phoscorite, while hydroxide-dominant PSM occur mainly in the axial carbonate-rich zone of the ore-pipe. Ti-rich PSM (up to oxycalciobetafite) occur in host silicate rocks and calcite carbonatite veins, and Ta-rich phases (up to microlites) are spread in intermediate and axial magnetite-rich phoscorite. In marginal (apatite)-forsterite phoscorite, there are only Ca-dominant PSM, and the rest of the rocks include Ca-, Na-and vacancy-dominant phases. The crystal structures of oxycalciopyrochlore and hydroxynatropyrochlore were refined in the Fd3m space group with R 1 values of 0.032 and 0.054 respectively. The total difference in scattering parameters of B sites are in agreement with substitution scheme B Ti 4+ + Y OH − = B Nb 5+ + Y O 2−. The perspective process flow diagram for rare-metal "anomalous ore" processing includes sulfur-acidic cleaning of baddeleyite concentrate from PSM and zirconolite-laachite impurities followed by deep metal recovery from baddeleyite concentrate and Nb-Ta-Zr-U-Th-rich sulfatic product from its cleaning.
“…One part of the PSM is formed in situ as rims around baddeleyite grains, and the other part is crystallized as individual crystals in carbonatites that act as a geochemical barrier for Nb(OH) 3 F 2 , Ta(OH) 3 F 3 + and other HFSE complexes [46,47]. Besides zirconolite-laachite, the typical PSM associated minerals in carbonate-rich rocks include Sc-phosphates juonniite and kampelite [27,48] Since Sc-Nb-rich baddeleyite and U-Ta-rich PSM of the ore-pipe axial zone contain most of the Kovdor's Nb, Ta, U, as well as a major part of Sc, this "Anomalous" zone can be regarded as a complex rare-metal deposit [6][7][8]. Prevailing close intergrowths of Sc-rich baddeleyite and U-rich kenopyrochlore significantly complicate the production of a high-quality baddeleyite concentrate.…”
The pyrochlore supergroup minerals (PSM) are typical secondary phases that replace (with zirconolite-laachite) earlier Sc-Nb-rich baddeleyite under the influence of F-bearing hydrothermal solutions, and form individual well-shaped crystals in surrounding carbonatites. Like primary Sc-Nb-rich baddeleyite, the PSM are concentrated in the axial carbonate-rich zone of the phoscorite-carbonatite complex, so their content, grain size and chemical diversity increase from the pipe margins to axis. There are 12 members of the PSM in the phoscorite-carbonatite complex. Fluorine-and oxygen-dominant phases are spread in host silicate rocks and marginal carbonate-poor phoscorite, while hydroxide-dominant PSM occur mainly in the axial carbonate-rich zone of the ore-pipe. Ti-rich PSM (up to oxycalciobetafite) occur in host silicate rocks and calcite carbonatite veins, and Ta-rich phases (up to microlites) are spread in intermediate and axial magnetite-rich phoscorite. In marginal (apatite)-forsterite phoscorite, there are only Ca-dominant PSM, and the rest of the rocks include Ca-, Na-and vacancy-dominant phases. The crystal structures of oxycalciopyrochlore and hydroxynatropyrochlore were refined in the Fd3m space group with R 1 values of 0.032 and 0.054 respectively. The total difference in scattering parameters of B sites are in agreement with substitution scheme B Ti 4+ + Y OH − = B Nb 5+ + Y O 2−. The perspective process flow diagram for rare-metal "anomalous ore" processing includes sulfur-acidic cleaning of baddeleyite concentrate from PSM and zirconolite-laachite impurities followed by deep metal recovery from baddeleyite concentrate and Nb-Ta-Zr-U-Th-rich sulfatic product from its cleaning.
“…The higher content of Nb and Sc in baddeleyite from the axial carbonate-rich phoscorite and carbonatite due to the 2Zr 4+ ↔ Sc 3+ + Nb 5+ substitution results in the intensive replacement of this mineral by pyrochlore-supergroup minerals (Fig. 6) accompanied by the formation of Sc phosphates (Yakovenchuk et al ., 2018): where Ap = hydroxylapatite; Bdy’ = Sc–Nb end-member of baddeleyite, Sc 0.5 Nb 0.5 O 2 ; Cal = calcite, Dol = dolomite; Jnn = juonniite, CaMgScP 2 O 8 (OH)·4H 2 O; and Pcl = pyrochlore-supergroup member with formula NaCaNb 2 O 6 (OH). Fig.…”
Hydroxynatropyrochlore, (Na,Сa,Ce)2Nb2O6(OH), is a new Na–Nb–OH-dominant member of the pyrochlore supergroup from the Kovdor phoscorite–carbonatite pipe, Kola Peninsula, Russia. It is cubic, Fd$\bar{3}$m, a = 10.3211(3) Å, V = 1099.46(8) Å3 and Z = 8 (from powder diffraction data) or a = 10.3276(5) Å, V = 1101.5(2) Å3 and Z = 8 (from single-crystal diffraction data). Hydroxynatropyrochlore is a characteristic accessory mineral of the low-carbonate phoscorite in the contact zone of the phoscorite–carbonatite pipe with host foidolite as well as in the carbonate-rich phoscorite and carbonatite of the pipe axial zone. It usually forms zonal cubic or cubooctahedral crystals (up to 0.5 mm in diameter) with irregularly shaped relics of amorphous U–Ta-rich hydroxykenopyrochlore inside. Characteristic associated minerals include rock-forming calcite, dolomite, forsterite, hydroxylapatite, magnetite and phlogopite, accessory baddeleyite, baryte, barytocalcite, chalcopyrite, chamosite–clinochlore, galena, gladiusite, juonniite, ilmenite, magnesite, pyrite, pyrrhotite, quintinite, spinel, strontianite, valleriite and zirconolite. Hydroxynatropyrochlore is pale brown, with an adamantine to greasy lustre and a white streak. The cleavage is average on {111} and the fracture is conchoidal. Mohs hardness is ~5. In transmitted light, the mineral is light brown, isotropic and n = 2.10(5) (λ = 589 nm). The calculated and measured densities are 4.77 and 4.60(5) g cm−3, respectively. The mean chemical composition determined by electron microprobe is: F 0.05, Na2O 7.97, CaO 10.38, TiO2 4.71, FeO 0.42, Nb2O5 56.44, Ce2O3 3.56, Ta2O5 4.73, ThO2 5.73, UO2 3.66, total 97.65 wt.%. The empirical formula calculated on the basis of Nb + Ta + Ti = 2 apfu is (Na1.02Ca0.73Ce0.09Th0.09 U0.05${\rm Fe}_{{\rm 0}{\rm. 02}}^{2 +} $)Σ2.00(Nb1.68Ti0.23Ta0.09)Σ2.00O6.03(OH1.04F0.01)Σ1.05. The simplified formula is (Na,Ca,Ce)2Nb2O6(OH). The mineral dissolves slowly in hot HCl. The strongest X-ray powder-diffraction lines [listed as (d in Å)(I)(hkl)] are as follows: 5.96(47)(111), 3.110(30)(311), 2.580(100)(222), 2.368(19)(400), 1.9875(6)(333), 1.8257(25)(440) and 1.5561(14)(622). The crystal structure of hydroxynatropyrochlore was refined to R1 = 0.026 on the basis of 80 unique observed reflections. The mineral belongs to the pyrochlore structure type A2B2O6Y1 with octahedral framework of corner-sharing BO6 octahedra with A cations and OH groups in the interstices. The Raman spectrum of hydroxynatropyrochlore contains characteristic bands of the lattice, BO6, B–O and O–H vibrations and no characteristic bands of the H2O vibrations. Within the Kovdor phoscorite–carbonatite pipe, hydroxynatropyrochlore is the latest hydrothermal mineral of the pyrochlore supergroup, which forms external rims around grains of earlier U-rich hydroxykenopyrochlore and separated crystals in voids of dolomite carbonatite veins. The mineral is named in accordance with the pyrochlore supergroup nomenclature.
“…Звёздочка -место находки кампелита. 4.00 , который хорошо соотносится с эмпирической формулой минерала.…”
Section: фиц кнц ранunclassified
“…1), где он в виде двух хрупких серебристо-белых сферолитов (до 1.5 мм в диаметре), сложенных его бесцветными пластинчатыми кристаллами (рис. 2), нарастает на хорошо образованные оранжевые кристаллы квинтинита-2Н в ассоциации с кальцитом, бобьеритом, пири-том и квинтинитом-3R [4]. Сами фоскориты, помимо кальцита (около 15 об.…”
Скандий как стратегический редкоземельный металл находит всё более широкое примене-ние в электронике, оптической, автомобильной и авиационной промышленности. В России одним из крупных его источников является Ковдорское месторождение магнетита, апатита и бадделеита [1,2]. Основным концентратором скандия является бадделеит, который включает этот металл по схеме 2Zr4+ ↔ Sc 3+ Nb 5+ [3]. Содержание ниобия и скандия в бадделеите последовательно возраста-ет от краевой части трубки, сложенной (апатит)-форстеритовыми фоскоритами, к промежуточной зоне бескарбонатных существенно магнетитовых фоскоритов и, далее, к осевой зоне карбонатсо-держащих фоскоритов и карбонатитов (рис. 1). Состав сосуществующего гидроксилапатита изме-няется в том же направлении по схеме Ca 2+ ↔ (Ba, Sr) 2+ [3], причём с глубиной количество бария за-метно увеличивается.При гидротермальном изменении Sc-Nb-содержащего бадделеита и Ba-содержащего ги-дроксилапатита происходит образование цирконолита (концентратор Zr), минералов груп-пы пирохлора (концентраторы Nb) и скандиевых фосфатов (концентраторы скандия) ёнаита, CaMgSc(PO 4 ) 2 (OH)·4H 2 O, и кампелита, Ba 3 Mg 1.5 Sc 4 (PO 4 ) 6 (OH) 3 ·4H 2 O по схематическим реакциям [4]: 12Bdy' + 6Dol + 4Ap +25H 2 O + 2CO 2 → 6Jnn+ 3Pcl + 14Cal и 16Bdy' + 3Dol + 4Ap + 9H 2 O + 9CO 2 + 5O 2 + 6Ba 2+ → 2Kam + 4Pcl + 15Cal, где Ap -гидроксилапатит; Bdy' -Sc-Nb минал бадделеита, Sc 0.5 Nb 0.5 O 2 ; Cal -кальцит, Dol -доло-мит; Jnn -ёнаит; Kam -кампелит, Pcl -пирохлор, Ca 2 NbO 7 . В отличие от сравнительно широко распространённого ёнаита [5], кампелит чрезвычайно ре-док и пока обнаружен в одной единственной пустоте в кальцито-магнетитовых фоскоритах на го-ризонте -100 м (см. рис. 1), где он в виде двух хрупких серебристо-белых сферолитов (до 1.5 мм в диаметре), сложенных его бесцветными пластинчатыми кристаллами (рис. 2), нарастает на хорошо образованные оранжевые кристаллы квинтинита-2Н в ассоциации с кальцитом, бобьеритом, пири-том и квинтинитом-3R [4]. Сами фоскориты, помимо кальцита (около 15 об. %) и магнетита (около Рис. 1. Изменение содержание ниобия и скандия в бадделеите, а также встречаемость апобадделеитового пирох-лора на горизонте -100 м Ковдорской фоскорит-карбонатитовой трубки. Звёздочка -место находки кампелита.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
