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GEOREF RECORD

Kentbrooksite from the Kangerdlugssuaq intrusion, East Greenland, a new Mn-Ree-Nb-F end-member in a series within the eudialyte group; description and crystal structure

Ole Johnsen, Joel D. Grice and Robert A. Gault
Kentbrooksite from the Kangerdlugssuaq intrusion, East Greenland, a new Mn-Ree-Nb-F end-member in a series within the eudialyte group; description and crystal structure
European Journal of Mineralogy (April 1998) 10 (2): 207-219

Abstract

Kentbrooksite occurs in alkaline pegmatitic bodies cutting pulaskite, and is associated with alkali feldspar, nepheline and Zr- and Ti-rich minerals such as kupletskite, lavenite, catapleiite, hjortdahlite and eudialyte. It forms anhedral to subhedral aggregates up to 2 cm and is transparent, yellow-brown, with a vitreous lustre; H. 5-6; D 3.10 g/cm (super 3) ; epsilon 1.623, Omega 1.628, non-pleochroic and no cleavage. EPMA results indicate an ideal formula (Na, REE) (sub 15) (Ca,REE) (sub 6) Mn (sub 3) Zr (sub 3) NbSi (sub 25) O (sub 74) F (sub 2<P6M><P255>2H) (sub 2) O; the IR spectrum is given. XRD powder data are tabulated; strongest lines 2.839(100), 2.961(91), 11.384(43), 7.088(41), 3.380(37) Aa; a 14.1686, c 30.0847 Aa, Z = 3; space group R3m. The structure has been refined to R 4.1%; kentbrooksite belongs to the eudialyte group and has the characteristic framework for this group, with three-membered and nine-membered rings of SiO (sub 4) tetrahedra cross-linked by Zr and M1 in octahedral coordination; important differences to eudialyte are (super [5]) Mn substituting for (super [4]) Fe in M2, (super [6]) Nb(M3) substituting for (super [4]) Si(M4), a high content of REE and F substituting for Cl. Kentbrooksite thus represents the Sigma Nb, REE, Mn, F end-member of a series within the eudialyte. The name is to honour C. Kent Brooks in acknowledgement of his leadership of 14 geological expeditions to the Kangerdlugssuaq area.


ISSN: 0935-1221
Serial Title: European Journal of Mineralogy
Serial Volume: 10
Serial Issue: 2
Title: Kentbrooksite from the Kangerdlugssuaq intrusion, East Greenland, a new Mn-Ree-Nb-F end-member in a series within the eudialyte group; description and crystal structure
Affiliation: University of Copenhagen, Geological Museum, Copenhagen, Denmark
Pages: 207-219
Published: 199804
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 18
Accession Number: 1998-032473
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 6 tables
Secondary Affiliation: Canadian Museum of Nature, Ottawa, ON, CAN, Canada
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United KingdomTwickenhamUKUnited Kingdom
Update Code: 199813
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