Fe-rich olenite with tetrahedrally coordinated Fe (super 3+) from Eibenstein, Austria; structural, chemical, and Moessbauer data

A dark green Fe-rich ( approximately 7 wt % FeO (sub tot) ) and Mn-bearing olenite from a beryl-bearing pegmatite near Eibenstein, Lower Austria, is reported. EPMA results indicate a deficiency in Si, but tetrahedrally coordinated B was not found. Moessbauer analysis shows that 90 % of the total Fe content occurs as (super [6]) Fe (super 2+) ( approximately 0.8 pfu) at the Y site, and 10 % occurs as Fe (super 3+) ( approximately 0.1 pfu) at the T site. The optimized formula calculated from chemical and structural data is (super X) (Na (sub 0.52) Ca (sub 0.01) [] (sub 0.47) ) (super Y) (Al (sub 1.62) Fe (super 2+) (sub 0.83) Mn (super 2+) (sub 0.42) Li (sub 0.05) Ti (super 4+) (sub 0.03) [] (sub 0.05) ) (super Z) (Al (sub 5.87) Mg (sub 0.13) ) (super T) (Si (sub 5.73) Al (sub 0.17) Fe (super 3+) (sub 0.10) )O (sub 18) (BO (sub 3) ) (sub 3) [(OH) (sub 3.32) O (sub 0.54) F (sub 0.14) ]. The structure was refined to R 0.022; a 15.938, c 7.1361 Aa, space group R3m. The T-O bond length is 1.624 Aa, in accord with the assigned site populations: (Si (sub 5.73) Al (sub 0.17) Fe (super 3+) (sub 0.10) ). This is the first example reported of olenite with tetrahedrally coordinated Fe (super 3+) . The Li content (Li 0.05 pfu) is uncommonly low for an Al-rich, Mg-poor tourmaline ( approximately 0.1 pfu Mg). This is attributed to the O(1) site being mainly occupied by O (super 2-) .