Details

Autor(en) / Beteiligte

• Kasatkin, A.V.
• Pekov, I.V.
• Škoda, R.
• Chukanov, N.V.
• Nestola, F.
• Agakhanov, A.A.
• Kuznetsov, A.M.
• Koshlyakova, N.N.
• Plášil, J.
• Britvin, S.N.

Titel

Fluorpyromorphite, Pb5(PO4)3F, a new apatite-group mineral from Sukhovyaz Mountain, Southern Urals, and Tolbachik volcano, Kamchatka

Ist Teil von

• Journal of geosciences (Prague), 2023-01, Vol.68 (1), p.81-93

Ort / Verlag

Prague: Czech Geological Society

Erscheinungsjahr

2023

Quelle

EZB Electronic Journals Library

Beschreibungen/Notizen

• Fluorpyromorphite, ideally Pb5(PO4)3F, a new apatite-group member, an F-dominant analog of pyromorphite and hydroxylpyromorphite. It is a supergene mineral found at two localities: Sukhovyaz Mountain, Ufaley District, Southern Urals (holotype) and Mountain 1004, Tolbachik volcano, Kamchatka (co-type), both in Russia. At Sukhovyaz, fluorpyromorphite forms anhedral grains up to 0.2 mm across (usually much smaller), filling cavities in quartz and sometimes partially replacing fluorapatite. Associated supergene minerals include pyromorphite, hydroxylpyromorphite, fluorphosphohedyphane, mimetite, and nickeltsumcorite. At Tolbachik, fluorpyromorphite occurs in the oxidation zone of paleo-fumarolic deposits in close association with pyromorphite, fluorphosphohedyphane, wulfenite, cerussite, munakataite, vanadinite, chrysocolla, and opal. It forms crude long-prismatic to acicular crystals up to 0.1 mm long and up to 5 pm thick combined in bunches and spherulites up to 0.2 mm. Fluorpyromorphite is colorless (Sukhovyaz) or yellow (Tolbachik), translucent to transparent and has a vitreous luster. It is brittle, with an uneven fracture and poor cleavage on (001). The calculated density values are 7.382 (holotype) and 6.831 (cotype) g/cm3. Fluorpyromorphite is optically uniaxial (-). In reflected light, it is light-grey, weakly anisotropic. The reflectance values (Rmin/Rmax, %) are: 15.8/16.6 (470 nm), 16.2/17.2 (546 nm), 15.9/16.9 (589 nm), 15.4/16.2 (650 nm). The chemical composition is (electron microprobe, wt. %; holotype/co-type): CaO 0.10/3.16, SrO 0.17/0.00, PbO 83.51/77.39, P2O5 16.13/16.35, CrO3 0.00/0.49, SeO3 0.00/0.98, F 1.00/1.35, Cl 0.29/0.40, H2Ocalc 0.13/0.00, -O=(F,Cl) -0.49/-0.66, total 100.84/99.46. The empirical formulae based on 13 anions (O + F + Cl + OH)pfu aie Pb4.95Ca0.02Sr0.02P3.00O,2F0 70(OH)0.,9Cl0.,, (holotype) and Pb4.MC\ň9P2.83Se6+0.09Cr6+0.0S O.. 99F087Cl014 (co-type). Fluorpyromorphite is hexagonal, space group P63/m, unit-cell parameters (trom powder X-ray diffraction data; holotype / co-type) are: a = 9.779(5) / 9.732(1), c = 7.241(9) / 7.242(1) Å, V = 599.6(7) / 594.0(2) Å3, and Z = 2. The crystal structure was refined using the Rietveld method to Rp= 0.1764 (holotype). Fluorpyromorphite is isostructural with other members of the apatite group, a subdivision of the apatite supergroup.