Zhanghuifenite, Na3Mn42+Mg2Al(PO4)6, a new mineral isostructural with bobfergusonite, from the Santa Ana mine, San Luis province, Argentina

Abstract

A new mineral species, zhanghuifenite, ideally Na 3 Mn 2+ 4 Mg 2 Al(PO 4) 6 , has been 18 found in the Santa Ana mine, San Luis province, Argentina. It occurs in irregular veinlets 19 or patches, 5 mm thick, in a nodule of beusite interlaminated with lithiophilite. Broken 20 pieces of zhanghuifenite are blocky or tabular. Single crystals are up to 0.8 x 0.5 x 0.5 21 mm. No twinning or parting is observed macroscopically. The mineral is deep green, 22 transparent with pale green streak and vitreous luster. It is brittle and has a Mohs 23 hardness of ~5 with good cleavage on {010}. The measured and calculated densities are 24 3.63(2) and 3.62 g/cm 3 , respectively. Optically, zhanghuifenite is biaxial (+), with α = 25 1.675 (2), β = 1.680 (2), γ = 1.690 (2) (white light), 2V (meas.) = 74(2)º, and 2V (calc.) = 26 71º. The calculated compatibility index based on the empirical formula is 0.020 27 (excellent). An electron microprobe analysis yields an empirical formula (based on 24 O 28 apfu) 29 (Na 2.80 Ca 0.11) Σ2.91 (Mn 2+ 3.09 Fe 2+ 0.47 Mg 0.36) Σ3.92 (Mg 1.31 Fe 2+ 0.69) Σ2.00 (Al 0.81 Fe 3+ 0.19)(PO 4) 6. 30 Zhanghuifenite is insoluble in water or hydrochloric acid. 31 This is the peer-reviewed, final accepted version for American Mineralogist, published by the Mineralogical Society of America. The published version is subject to change. Cite as Authors (Year) Title. American Mineralogist, in press.