Hatertite, Na (sub 2) (Ca,Na)(Fe (super 3+) ,Cu) (sub 2) (AsO (sub 4) ) (sub 3) , a new alluaudite-group mineral from Tolbachik fumaroles, Kamchatka Peninsula, Russia

Hatertite, ideally Na (sub 2) (Ca, Na)(Fe (super 3+) , Cu) (sub 2) (AsO (sub 4) ) (sub 3) , was found in a fumarole of the North Breach of the Great fissure Tolbachik volcano eruption (1975-1976), Kamchatka Peninsula, Russia. The mineral occurs as individual, prismatic and tabular, honey-yellow crystals up to 0.3 mm across. It has a vitreous luster and yellow streak. Hatertite is monoclinic, C2/c, a = 12.590(2), b = 12.993(3), c =6.700(2) Aa, beta =113.72(2) degrees , V = 1003.4(3) Aa (super 3) , Z =4, D (sub calc) = 4.06 g/cm (super 3) . The eight strongest lines of the powder X-ray diffraction pattern are [d (sub obs) in Aa (I) (hkl)]: 6.493(25)(020); 3.628 (25)(131); 3.204(39)( 112,131); 3.065(18)(002); 2.976(28)(312, 222); 2.830(100)(240), 2.632(36)(132); 1.647(19)(204,640). Hatertite is optically positive, alpha = 1.820(3), beta = 1.825(3), gamma = 1.833(3), 2V (sub meas.) = 60(10) degrees , 2V (sub calc.) = 77 degrees . The orientation is Y = b. The chemical composition determined by the electron-microprobe analysis is as follows (wt.%): Na (sub 2) O 8.49, K (sub 2) O 2.41, MnO 1.64, CaO 7.06, Fe (sub 2) O (sub 3) 11.15, ZnO 2.05, CuO 8.10, Al (sub 2) O (sub 3) 2.22, As (sub 2) O (sub 5) 55.67, total 98.79. The empirical formula (based on 12 O apfu) is (Na (sub 0.47) K (sub 0.32) )(Na (sub 0.84) Ca (sub 0.16) ) (Ca (sub 0.62) Na (sub 0.19) Zn (sub 0.16) Mn (sub 0.14) ) (Fe (super 3+) (sub 0.44) Cu (sub 0.32) Al (sub 0.13) Na (sub 0.11) ) (sub 2) (As (sub 1.01) O (sub 4) ) (sub 3) . A general crystal chemical formula for hatertite should be written as NaNa(Ca (sub 1-x) M (super +) (sub x) )(Fe (super 3+) (sub 1+x) M (super 2+) (sub 1-x) )(AsO (sub 4) ) (sub 3) , where 0.5 > X >0, M (super +) is an unspecified monovalent cation, and M (super 2+) is an unspecified divalent cation. The crystal structure was solved by direct methods and refined to an agreement index R1 = 0.028 on the basis of 751 independent observed reflections. Hatertite is a new arsenate member of the alluaudite group. Its structure is based upon chains of edge-sharing octahedra running along [-101] and linked by T(2)O (sub 4) tetrahedra into layers parallel to (010). The layers are further interlinked through T(1)O (sub 4) tetrahedra to form a three-dimensional octahedral-tetrahedral framework with the A(1) and A(2)' sites in the interstices. The mineral was named in honor of Prof. Frederic Hatert (b. 1973), University of Liege, Belgium, for his contributions to the mineralogy and crystal chemistry of alluaudite-group minerals.