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Bobcookite, NaAl(UO (sub 2) ) (sub 2) (SO (sub 4) ) (sub 4) .18H (sub 2) O and wetherillite, Na (sub 2) Mg(UO (sub 2) ) (sub 2) (SO (sub 4) ) (sub 4) .18H (sub 2) O, two new uranyl sulfate minerals from the Blue Lizard Mine, San Juan County, Utah, USA

Anthony R. Kampf, Jakub Plasil, Anatoly V. Kasatkin and Joe Marty
Bobcookite, NaAl(UO (sub 2) ) (sub 2) (SO (sub 4) ) (sub 4) .18H (sub 2) O and wetherillite, Na (sub 2) Mg(UO (sub 2) ) (sub 2) (SO (sub 4) ) (sub 4) .18H (sub 2) O, two new uranyl sulfate minerals from the Blue Lizard Mine, San Juan County, Utah, USA
Mineralogical Magazine (June 2015) 79 (3): 695-714

Abstract

The new minerals bobcookite (IMA 2014-030), NaAl(UO (sub 2) ) (sub 2) (SO (sub 4) ) (sub 4) .18H (sub 2) O and wetherillite (IMA 2014-044), Na (sub 2) Mg(UO (sub 2) ) (sub 2) (SO (sub 4) ) (sub 4) .18H (sub 2) O, were found in the Blue Lizard mine, San Juan County, Utah, USA, where they occur together as secondary alteration phases in association with boyleite, chalcanthite, dietrichite, gypsum, hexahydrite, johannite, pickeringite and rozenite. Bobcookite descriptive details: lime green to greenish-yellow massive veins and columnar crystals; transparent; vitreous lustre; bright greenish-white fluorescence; pale greenish yellow streak; hardness (Mohs) 21/2; brittle; conchoidal fracture; no cleavage; moderately hygroscopic; easily soluble in cold H (sub 2) O; density (sub calc) =2.669 g cm (super -3) . Optically, biaxial (-), alpha =1.501(1), beta =1.523(1), gamma =1.536(1) (white light); 2V (sub meas.) =78(1) degrees ; 2V (sub calc.) =74 degrees ; dispersion r<v, moderate. Pleochroism: X colourless, Y very pale yellow-green, Z pale yellow-green; X<Y<Z. EDS analyses yielded the empirical formula Na (sub 0.97) Al (sub 1.09) (U (sub 1.02) O (sub 2) ) (sub 2) (S (sub 0.98) O (sub 4) ) (sub 4) (H (sub 2) O) (sub 18) . Bobcookite is triclinic, P1, a=7.7912(2), b=10.5491(3), c=11.2451(8) Aa, alpha =68.961(5), beta =70.909(5), gamma = 87.139(6) degrees , V=812.79(8) Aa (super 3) and Z=1. The structure (R (sub 1) =1.65% for 3580 F (sub o) >4sigma F) contains [(UO (sub 2) )(SO (sub 4) ) (sub 2) (H (sub 2) O)] chains linked by NaO (sub 4) (H (sub 2) O) (sub 2) octahedra to form layers. Hydrogen bonds to insular Al(H (sub 2) O) (sub 6) octahedra and isolated H (sub 2) O groups hold the structure together. The mineral is named for Dr Robert (Bob) B. Cook of Auburn University, Alabama, USA. Wetherillite descriptive details: pale greenish-yellow blades; transparent; vitreous lustre; white streak; hardness (Mohs) 2; brittle; two cleavages, {101} perfect and {010} fair; conchoidal or curved fracture; easily soluble in cold H (sub 2) O; density (sub calc) =2.626 g cm (super -3) . Optically, biaxial (+), alpha =1.498(1), beta =1.508(1), gamma =1.519(1) (white light); 2V (sub meas.) =88(1) degrees , 2V (sub calc.) =87.9 degrees ; dispersion is r<v, distinct; optical orientation: Z=b, X (sub a) =54 degrees in obtuse beta ; pleochroism: X colourless, Y pale yellow-green, Z pale yellow-green; X<Y congruent to Z. EDS analyses yielded the empirical formula Na (sub 1.98) (Mg (sub 0.58) Zn (sub 0.24) Cu (sub 0.11) Fe (super 2+) (sub 0.09) ) (sub Sigma 1.02) (U (sub 1.04) O (sub 2) ) (sub 2) (S (sub 0.98) O (sub 4) ) (sub 4) (H (sub 2) O) (sub 18) . Wetherillite is monoclinic, P2 (sub 1) /c, a=20.367(1), b=6.8329(1), c=12.903(3) Aa, beta =107.879(10) degrees , V=1709.0(5) Aa (super 3) and Z=2. The structure (R (sub 1) =1.39% for 3625 F (sub o) >4sigma F) contains [(UO (sub 2) )(SO (sub 4) ) (sub 2) (H (sub 2) O)] sheets parallel to {100}. Edge-sharing chains of Na(H (sub 2) O) (sub 5) O polyhedra link adjacent uranyl sulfate sheets forming a weakly bonded three-layer sandwich. The sandwich layers are linked to one another by hydrogen bonds through insular Mg(H (sub 2) O) (sub 6) octahedra and isolated H (sub 2) O groups. The mineral is named for John Wetherill (1866-1944) and George W. Wetherill (1925-2006).


ISSN: 0026-461X
EISSN: 1471-8022
Coden: MNLMBB
Serial Title: Mineralogical Magazine
Serial Volume: 79
Serial Issue: 3
Title: Bobcookite, NaAl(UO (sub 2) ) (sub 2) (SO (sub 4) ) (sub 4) .18H (sub 2) O and wetherillite, Na (sub 2) Mg(UO (sub 2) ) (sub 2) (SO (sub 4) ) (sub 4) .18H (sub 2) O, two new uranyl sulfate minerals from the Blue Lizard Mine, San Juan County, Utah, USA
Affiliation: Natural History Museum of Los Angeles County, Mineral Sciences Department, Los Angeles, CA, United States
Pages: 695-714
Published: 201506
Text Language: English
Publisher: Mineralogical Society, London, United Kingdom
References: 34
Accession Number: 2016-007020
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 6 tables
N37°00'00" - N38°30'00", W111°13'00" - W109°02'60"
Secondary Affiliation: Academy of Sciences of the Czech Republic, CZE, Czech RepublicRussian Academy of Sciences, RUS, Russian Federation
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Mineralogical Society of Great Britain and Ireland. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201604
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