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Floerkeite, K (sub 3) Ca (sub 2) Na[Al (sub 8) Si (sub 8) O (sub 32) ].12H (sub 2) O, a new phillipsite-type zeolite from the Bellerberg, east Eifel volcanic area, Germany

Christian L. Lengauer, Uwe Kolitsch and Ekkehart Tillmanns
Floerkeite, K (sub 3) Ca (sub 2) Na[Al (sub 8) Si (sub 8) O (sub 32) ].12H (sub 2) O, a new phillipsite-type zeolite from the Bellerberg, east Eifel volcanic area, Germany
European Journal of Mineralogy (August 2009) 21 (4): 901-913


Florkeite is a new phillipsite-type zeolite. It was found in a Ca-rich xenolith from a quarry at the Bellerberg volcano near Ettringen, East Eifel volcanic area, Germany. The paragenesis includes tobermorite, thaumasite, willhendersonite, gismondine and ellestadite. It forms subparallel, short prismatic, pseudo-monoclinic crystals elongated along [100] and flattened on {010}, with a maximum length of 0.6 mm and a thickness of up to 0.1 mm. Additional forms are {100}, {001} and {201}. Florkeite is colourless, transparent, non-fluorescent and has a vitreous lustre and a white streak. It is brittle with irregular fracture, the calculated density is 2.266 gcm (super -3) . Optically, it is biaxial negative with n (sub alpha ) =1.506(2), n (sub beta ) =1.514(2), n (sub gamma ) =1.518(2), 2V=71.0(5) degrees at 589.3 nm and 297 K. No pleochroism is observed. Orientation of the indicatrix is X(circumflex)c=43 degrees , Y (circumflex) b=40 degrees and Z(circumflex)a=8 degrees . Electron microprobe analyses yielded (wt%): Na (sub 2) O 2.32, K (sub 2) O 10.29, MgO 0.04, CaO 8.43, Al (sub 2) O (sub 3) 30.20, SiO (sub 2) 35.29, sum 86.57. A H (sub 2) O content of 15.57 wt% was derived from the single-crystal structure refinement. The empirical formula calculated on the basis of Al+Si=16 pfu is K (sub 2.96) Ca (sub 2.04) Na (sub 1.02) Mg (sub 0.01) [Al (sub 8.03) Si (sub 7.97) O (sub 31.97) ].11.72H (sub 2) O and the ideal formula can be given as K (sub 3) Ca (sub 2) Na[Al (sub 8) Si (sub 8) O (sub 32) ].12H (sub 2) O. Florkeite is triclinic, space-group P1 (no. 2), the unit-cell parameters in phillipsite-type setting are a=19.965(1), b=14.274(1), c=8.704(1) Aa, alpha =88.37(1), beta = 125.08(1), gamma =89.57(1) degrees , V=2028.2(3) Aa (super 3) , Z=2 and the a:b:c ratio is 1.399:1:0.610. The five strongest lines in the powder X-ray diffraction pattern are (d in Aa/I (sub obs) ): 3.235/100, 3.162/80, 3.135/80, 2.736/60, 4.956/45. The single-crystal structure refinement (R1=4.39%) confirmed that the structure of florkeite is the triclinically distorted analogue of phillipsite with a complete (Al, Si) ordering at the T-sites of the framework (mean T(Al)-O: 1.731-1.743 Aa and T(Si)-O: 1.615-1.631 Aa), which reduces the topochemical symmetry to B2/b. The K (super +) cations are placed near the centre of 8-rings of the oto units, the Ca (super 2+) and Na (super +) cations are located within the phi units. The doubling of the a-parameter and the reduction of the real symmetry to P1 (is caused by an ordering of the extra-framework cations and H (sub 2) O molecules within the 8-ring channel system along [100], basically Ca-[]-Ca, Na-Ca-Na and H (sub 2) O-K-H (sub 2) O. The (Al, Si) ordering is attributed to low-thermal genetic conditions within the Ca-rich xenolithic host, also indicated by the paragenesis with willhendersonite. Holotype material of florkeite has been deposited at the mineral collection of the Naturhistorisches Museum Wien, Austria. The mineral is named in honour of the German mineralogist and crystallographer Otto Wilhelm Florke (born 1926).

ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 21
Serial Issue: 4
Title: Floerkeite, K (sub 3) Ca (sub 2) Na[Al (sub 8) Si (sub 8) O (sub 32) ].12H (sub 2) O, a new phillipsite-type zeolite from the Bellerberg, east Eifel volcanic area, Germany
Affiliation: Universitaet Wien, Institut fuer Mineralogie und Kristallographie, Vienna, Austria
Pages: 901-913
Published: 200908
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 45
Accession Number: 2009-085456
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 7 tables
N50°00'00" - N50°30'00", E06°19'60" - E07°19'60"
N49°00'00" - N51°00'00", E06°10'00" - E08°30'00"
Secondary Affiliation: Naturhistorisches Museum, AUT, Austria
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Schweizerbart'sche Verlagsbuchhandlung. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 200946
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