Abstract

Well-crystallized euhedral crystals of aluminian lizardite-2H 2 (Mg (sub 2.35) Fe (super 2+) (sub 0.06) Fe (super 3+) (sub 0.07) Al (sub 0.52) ) (Si (sub 1.41) Al (sub 0.59) )O (sub 5.00) (OH) (sub 4.00) were found near Schio (Vicenza, Italy). To gain insight into the role of a high Al content lizardite, chemical analyses and single-crystal X-ray data collection were conducted. Structure refinement, completed in space group P6 3 (agreement factor R = 0.034), gives mean T-O values of 1.654 Aa and 1.664 Aa for T1 and T2 sites, respectively. The ditrigonal distortion of the six-membered tetrahedral ring is positive (alpha = +9.7 degrees ), as expected for the 2H 2 polytype. The octahedral site has a mean bond length similar to that of the Mg-rich octahedra of amesite and distortion parameters similar to those of Al-rich octahedra.

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