Fehér Béla (szerk.): Az ásványok vonzásában, Tanulmányok a 60 éves Szakáll Sándor tiszteletére (Miskolc, 2014)
Ozdín Daniel - Szakáll Sándor: A Miskolc-lillafüredi axinit-(Fe) kémiai összetétele
204 D. Ozdín & S. Szakáll (2008) to axinite-(Fe), axinite-(Mg), axinite-(Mn), respectively. The first classification of the axinite group, which included three basic minerals, was done by Sanero & Gottardi (1968). According to these authors the revised general chemical formula is (Ca,Mn)4(Mn,Fe,Mg)2Al4B2Si8O30(OH)2. A newly described mineral “magnesio-axinite” from Merelani Hills in Tanzania was later also included in this group (Jobbins et al., 1975). Lumpkin and Ribbe (1979) suggested structural formula [61[(Mn,Fe2+,Mg,Zn,Alw)(Ca2_x Mnx)(Al2_yFe3+y)]2(OH2^wOw)141(B2Si8_zAlz)O30, where w < 1, x < 1, y « 1, and z « 1, however this formula has a number of structural deficiencies, which have been mentioned by Andreozzi et al. (2000). Andreozzi et al. (2000) dealt with crystal chemistry of axinite group and proposed the crystallochemical formula for this group as following: l6)[Ca (Ca1_xMnx)(Mn,Fe2+,Mg,Zn,Alu,Fe3+v) 5>](Al2_yFe3+y)]2[4,[(Bi_zSiz)2Sig]O30(OH1_wOw)2, where x < 1, u < 1, v < 1, y < 1, z « 1, and w = (u + v + z). Andreozzi et al. (2004) proposed the final general crystallochemical formula of axinite group as VI[X1 X2 Y Z1 Z2]2IV[T1 T2 T3 T4 T5]2O30(OwOH1_w)2, where VI and IV are coordination numbers and: XI =Ca, (Na) X2 = Ca (in axinites) or Mn (in tinzenite) Y = Mn2+, Fe2+, Mg, (Al, Fe3+) Z1 = Al, Fe3+ Z2 = Al Tl, T2, T3 = Si T4 = Si, (B) T5 = B, (Si). Although the crystallochemical formula mentioned above is correct, CNMNC states on the list of existing IMA approved minerals in February 2013 (IMA, 2013) the following members of axinite group and their chemical formulas that should be used: Axinite-(Fe):Ca4Fe2+2Al4[B2Si8O30](OH)2 Axinite-(Mg): Ca4Mg2Al4[B2Si8O30](OH)2 Axinite-(Mn): Ca4Mn2+2Al4[B2Si8O30](OH)2 Tinzenite: Ca6Al4[B2Si8O30](OH)2. However, the listed formula of tinzenite is wrong, because in tinzenite manganese is the dominant cation at X2 and Y sites instead of calcium, therefore the correct crystallochemical formula should be Ca2(Mn,Ca)2Mn2+2Al4[B2Si8O30](OH)2. 2. Methods The samples containing axinite were studied by polarizing optical microscope and electron microprobe. Axinite specimens were first observed using thin sections in polarized light on the polarizing microscope Leica DM2500 R Electron-microprobe analyses (EMPA) were performed by a CAMECA SX100 microprobe with wavelength-dispersive spectrometers at the State Geological Institute of Dionyz Stúr in Bratislava. Operating conditions were as follows: accelerating voltage of 15 kV, beam current of 15 or 20 nA and beam diameter between 5 and 8 pm. Standards and lines included wollastonite (Si Ka, Ca Ka), Ti02 (Ti Ka), A1203 (Al Ka), pure Cr (Cr Ka), pure V (V Ka), fayalite (Fe Ka), rhodonite (Mn Ka), forsterite (Mg Ka), willemite
