Skip to Main Content
GEOREF RECORD

Fluorophlogopite from Biancavilla (Mt. Etna, Sicily, Italy); crystal structure and crystal chemistry of a new F-dominant analog of phlogopite

Antonio Gianfagna, Fernando Scordari, Simona Mazziotti-Tagliani, Gennaro Ventruti and Luisa Ottolini
Fluorophlogopite from Biancavilla (Mt. Etna, Sicily, Italy); crystal structure and crystal chemistry of a new F-dominant analog of phlogopite
American Mineralogist (October 2007) 92 (10): 1601-1609

Abstract

Fluorophlogopite, a new F-dominant mineral of the mica group, was found at Monte Calvario, Biancavilla, lower southwestern flanks of Mt. Etna volcano (Catania, Sicily, Italy). The mineral occurs in autodasts of gray-red altered benmoreitic lavas, primarily associated with fluoro-edenite, alkali-feldspars, clino- and ortho-pyroxenes, fluorapatite, hematite, and pseudobrookite. It was formed by metasomatism of the original lava rocks from very hot fluid enriched in F, Cl, and other incompatible elements. Fluorophlogopite occurs as very thin laminae with a diameter of 200 to 400 mu m. Main physical properties are pale yellow in color; yellowish-white in thin section; vitreous to resinous luster; transparent; non-fluorescent; Mohs" hardness 2-3; brittle and malleable; perfect cleavage on {001}; biaxial (-), alpha (sub calc) = 1.5430(8), beta = 1.5682(5), gamma = 1.5688(5) (lambda = 589 nm); 2V (sub meas) = 17(2) degrees ; alpha = acute bisectrix (perpendicular) (001); nonpleochroic; D (sub calc) = 2.830 g/cm (super 3) (using empirical formula and single-crystal unit-cell parameters), D (sub calc) = 2.842 g/cm (super 3) (using empirical formula and powder cell constants). Infrared spectrum did not show a significant absorption band in the OH-stretching region (3800-3600 cm (super -l) ) confirming that the F content of the fluorophlogopite from Biancavilla is close to the stoichiometric value. Unit-cell parameters from X-ray powder-diffraction data (114.6 mm diameter Gandolfi camera, CuKalpha are a = 5.305(2), b = 9.189(3), c = 10.137(4) Aa, beta = 100.02(3) degrees . These data agree with those obtained by single-crystal X-ray studies on a very thin (approximately 15 mu m) fluorophlogopite crystal, i.e., Monoclinic (1M polytype); Space Group C2/m; a = 5.3094(4), b = 9.1933(7), c = 10.1437(8) Aa, beta = 100.062(5) degrees , V = 487.51(6) A (super 3) , Z = 2. Structure refinements using anisotropic displacement parameters converged at R = 3.50, R (sub w) = 4.37, R (sub sym) = 3.72%. Electron microprobe analysis performed on the same crystal used for X-ray investigation gave: SiO (sub 2) = 45.75(39), TiO (sub 2) = 1.05(5), Al (sub 2) O (sub 3) = 9.60(19), MgO = 27.92(30), MnO = 0.16(3), FeO (sub tot) = 1.25(6), BaO = 0.09(5), K (sub 2) O = 8.22(11), Na (sub 2) O = 0.61(30), Cl = 0.02(1) wt%. Secondary Ion Mass Spectrometry (SIMS) was used to estimate light elements [Li (sub 2) O = 0.30(1) and H (sub 2) O = 0.16(2) wt%] and fluorine content [F = 8.69(24) wt%]. The new mineral fluorophlogopite and its name were approved by IMA-CNMMN (2006/011).


ISSN: 0003-004X
EISSN: 1945-3027
Coden: AMMIAY
Serial Title: American Mineralogist
Serial Volume: 92
Serial Issue: 10
Title: Fluorophlogopite from Biancavilla (Mt. Etna, Sicily, Italy); crystal structure and crystal chemistry of a new F-dominant analog of phlogopite
Affiliation: Universita di Roma La Sapienza, Dipartimento di Scienze della Terra, Rome, Italy
Pages: 1601-1609
Published: 200710
Text Language: English
Publisher: Mineralogical Society of America, Washington, DC, United States
References: 52
Accession Number: 2007-117221
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 9 tables
N37°45'00" - N37°45'00", E15°01'00" - E15°01'00"
Secondary Affiliation: Universita di Bari, ITA, ItalyIstituto di Geoscienze e Georisorse Pavia, ITA, Italy
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Mineralogical Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 200748
Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal