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Ferrirockbridgeite, (Fe (sub 0.67) (super 3+) (sub 0.33) ) (sub 2) (Fe (super 3+) ) (sub 3) (PO (sub 4) ) (sub 3) (OH) (sub 4) (H (sub 2) O), and the oxidation mechanism for rockbridgeite-group minerals

Ian Edward Grey, Anthony R. Kampf, Erich Keck, John D. Cashion, Colin M. MacRae, Yesim Gozukara and Finlay L. Shanks
Ferrirockbridgeite, (Fe (sub 0.67) (super 3+) (sub 0.33) ) (sub 2) (Fe (super 3+) ) (sub 3) (PO (sub 4) ) (sub 3) (OH) (sub 4) (H (sub 2) O), and the oxidation mechanism for rockbridgeite-group minerals
European Journal of Mineralogy (March 2019) 31 (3): 585-594

Abstract

Ferrirockbridgeite, ideally (Fe (sub 0.67) (super 3+) (sub 0.33) ) (sub 2) (Fe (super 3+) ) (sub 3) (PO (sub 4) ) (sub 3) (OH) (sub 4) (H (sub 2) O), is a new member of the rockbridgeite group. The type specimen is from the Palermo No. 1 pegmatite in North Groton, Grafton County, New Hampshire, USA. Electron microprobe analysis, coupled with Mossbauer spectroscopy for FeO and thermogravimetric analysis (TGA) for H (sub 2) O gives the empirical formula Mn (sub 0.31) (super 2+) Fe (sub 0.08) (super 2+) Mg (sub 0.01) Zn (sub 0.03) Ca (sub 0.05) Fe (sub 4.18) (super 3+) P (sub 2.87) O (sub 17) H (sub 6.11) . Ferrirockbridgeite is orthorhombic, space group Bbmm with a = 13.853(1), b = 16.928(1), c = 5.1917(5) Aa and Z = 4. Optically, ferrirockbridgeite is biaxial (-), with alpha = 1.875(5), beta = 1.890(calc), gamma = 1.900(5) (measured in white light) and 2V (meas) is 78(1) degrees from extinction data. The dispersion is strong, with r > v. The optical orientation is X = c, Y = a, Z = b. The pleochroism is X = yellow brown, Y = olive brown, Z = dark olive green; Z > Y > X. Crystal structure refinements on ferrirockbridgeite and other oxidized rockbridgeite-group species, including type rockbridgeite and type frondelite, show that oxidation is accompanied by loss of Fe (super 2+) from the M2 site according to the reaction [3Fe (super 2+) ] --> [2Fe (super 3+) + ] + Fe (super 2+) (removed) +2e-. A variable portion of the Fe removed from the M2 site becomes trapped at M3 site vacancies. A general formula for oxidized rockbridgeite-group minerals is presented.


ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 31
Serial Issue: 3
Title: Ferrirockbridgeite, (Fe (sub 0.67) (super 3+) (sub 0.33) ) (sub 2) (Fe (super 3+) ) (sub 3) (PO (sub 4) ) (sub 3) (OH) (sub 4) (H (sub 2) O), and the oxidation mechanism for rockbridgeite-group minerals
Affiliation: CSIRO Mineral Resources, Clayton South, Victoria, Australia
Pages: 585-594
Published: 20190330
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Germany
References: 26
Accession Number: 2019-032168
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 7 tables
N43°45'02" - N43°45'02", W71°53'23" - W71°53'23"
Secondary Affiliation: Natural History Museum of Los Angeles County, USA, United StatesMonash University, AUS, AustraliaCSIRO Manufacturing, AUS, Australia
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Abstract, copyright, Schweizerbart'sche Verlagsbuchhandlung. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201917
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