Original paper

The behaviour of Mn in amphiboles: Mn in synthetic fluor-edenite and synthetic fluor-pargasite

Oberti, Roberta; Hawthorne, Frank C.; Raudsepp, Mati

European Journal of Mineralogy Volume 9 Number 1 (1996), p. 115 - 122

18 references

published: Dec 30, 1997
manuscript accepted: Oct 16, 1996
manuscript received: May 3, 1996

DOI: 10.1127/ejm/9/1/0115

BibTeX file

ArtNo. ESP147050901011, Price: 29.00 €

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Abstract

Abstract The crystal structures of two synthetic C2/m amphiboles, manganoan fluor-edenite Na1.06(Ca1.41Na0.12Mn0.47)(Mg4.44Mn0.411Al0.15)(Si6.91Al1.09)O22F2, a = 9.829(4), b = 18.024(9), c = 5.284(2) Å, ß = 104.66(2)°, and manganoan fluor-pargasite (Na0.96Ca0.13)(Ca1.51Mn0.49) (Mg3.47Mn0.73Al0.80)(Si5.95Al2.05)O22F2, a = 9.812(4), b = 17.926(6), c = 5.308(3) Å, ß = 105.10(3)°, have been refined to R indices of 2.0 % and 1.4 %, respectively, using MoKα X-ray data. Site-scattering refinement and electron-microprobe data both indicate that there is a large amount (~ 0.50 apfu) of Mn2+ at the M(4) site in each synthetic amphibole. C-group Mn2+ shows the ordering pattern M(2) » M(l) » M(3) in these amphiboles as in many natural sodic-calcic and alkali amphiboles. This behaviour is significantly different from that of Fe2+ which shows the ordering pattern M(l) ≤ M(3) in Mn-poor calcic, sodic-calcic and alkali amphiboles. The presence of significant Ca at the A site in F-rich pargasite is also confirmed

Keywords

amphibolecrystal-structure refinementmanganesesynthesis