2018
Horakite, a new hydrated bismuth uranyl-arsenate-phosphate mineral from Jachymov (Czech Republic) with a unique uranyl-anion topology
PLÁŠIL, Jakub, Anthony R KAMPF, Jiří SEJKORA, Jiří ČEJKA, Radek ŠKODA et. al.Základní údaje
Originální název
Horakite, a new hydrated bismuth uranyl-arsenate-phosphate mineral from Jachymov (Czech Republic) with a unique uranyl-anion topology
Autoři
PLÁŠIL, Jakub (203 Česká republika, garant), Anthony R KAMPF (840 Spojené státy), Jiří SEJKORA (203 Česká republika), Jiří ČEJKA, Radek ŠKODA (203 Česká republika, domácí) a Jaromír TVRDÝ (203 Česká republika, domácí)
Vydání
Journal of Geosciences, Prague, Czech Geological Society, 2018, 1802-6222
Další údaje
Jazyk
angličtina
Typ výsledku
Článek v odborném periodiku
Obor
10504 Mineralogy
Stát vydavatele
Česká republika
Utajení
není předmětem státního či obchodního tajemství
Odkazy
Impakt faktor
Impact factor: 1.275
Kód RIV
RIV/00216224:14310/18:00106223
Organizační jednotka
Přírodovědecká fakulta
UT WoS
000447813900004
Klíčová slova anglicky
horákite; new mineral; uranyl arsenate; crystal structure; topology; Jáchymov
Příznaky
Mezinárodní význam, Recenzováno
Změněno: 8. 4. 2020 13:12, Mgr. Marie Šípková, DiS.
Anotace
V originále
Horákite, ideally (Bi7O7OH)[(UO2)4(PO4)2(AsO4)2(OH)2]·3.5H2O, is a new uranyl mineral discovered on a specimen originating from Jáchymov, Czech Republic (most probably from the Geister vein, Rovnost mine). It occurs as a su-pergene alteration mineral in association with phosphuranylite (overgrowing older metatorbernite–metazeunerite) in a quartz gangue with abundant tennantite. Horákite forms greenish-yellow to pale yellow prismatic crystals clustering to acicular aggregates, up to 1 mm across. Crystals are transparent to translucent with a vitreous luster. The mineral has a light yellow streak. Estimated Mohs’ hardness is ~2. The cleavage is perfect on {100}. The calculated density is 6.358 g/cm3. Horákite is optically biaxial (+), alpha =approx 1.81, beta =approx 1.84, gamma =approx 1.88 (measured in white light); 2Vobs. is 78(1)°, 2Vcalc. is 83°; non-pleochroic. The optical orientation is X = b, Z =approx.c. Electron-microprobe analysis yielded the empirical formula (Bi7.01Pb0.14)O7OH[(U1.01O2)4(P1.03O4)2(As0.74Si0.23O4)2(OH)2]·3.5H2O based on 37.5 O apfu. Horákite is monoclinic, C2/c, a = 21.374(2), b = 15.451(3), c = 12.168(2) A, beta = 122.26(1)° and V = 3398.1(10) A3, Z = 4. The eight strongest X-ray powder-diffraction lines are [dobs A(I)(hkl)]: 11.77(100)(110), 6.21(23)(–202), 5.55(23)(310, –112), 4.19(27)(–331), 3.54(61)( 510, –423), 3.29(20)( 331), 3.14(58)(241, 023) and 3.02(98)(150, 113, –533, mult.). The crystal structure refinement of horákite, refined to R = 5.95 % for 1774 unique observed reflections, revealed a novel sheet structure. It consists of topologically unique [(UO2)4(PO4)2(AsO4)2(OH)2] sheets (i.e., horákite topology), and an interstitial {(Bi7O7OH)(H2O)3.5} complex. Sheets result from the polymerization of UO7 bipyramids by sharing edges to form tetrameric units; tetrahedrally coordinated sites are linked to the UO7 both monodentately (T1 to U1) and bidentately (T2 to U2). The mineral is named after František Horák (1882–1919), the mining engineer in Jáchymov, and his grandson, Vladimír Horák (born 1964), an amateur mineralogist and expert on the mining history of the Jáchymov ore district.