IMA2011-032 = Günterblassite

Sold at Ste Marie-aux-Mines show 2011.

(K,Ca,Ba,Na,[])3Fe[(Si,Al)13O25(OH,O)4].7H2O

Added.



Edited 1 time(s). Last edit at 08/03/2011 08:38AM by Uwe Kolitsch.

Well done! My best compliments to Gunter.

Congratulations Günter!!

Hi Harjo and Marco,

thanks for the congratulation!

best regards
Günter

Reference:
▪ Chukanov, N.V., Rastsvetaeva, R.K., Aksenov, S.M., Pekov, I.V., Britvin, S.N., Belakovskiy, D.I., Schüller, W., Ternes, B. (2012): Günterblassite, (К,Са)3-xFе[(Si,Аl)13O25(ОН,O)4]·7Н2O, a new mineral, the first phillosilicate with triple tetrahedral layer. Zapiski RMO, 141, 71-79.

Abstract:
A new mineral günterblassite has been found in the basalt quarry at Mount Rother Kopf, near the town Gerolstein, Eifel Mountains, Germany. It occurs in the late association including nepheline, leucite, augite, phlogopite, magnetite, perovskite, götzenite, lamprophyllite-group minerals, chabazite-K, chabazite-Ca, phillipsite-Ca and calcite. Flattened colorless crystals of günterblassite, up to 0.2 X 1 X 1.5 mm size, and their aggregates occur in miarolitic cavities in alkaline basalt. The mineral is brittle, with Mohs' hardness of 4. Cleavage is perfect on (001), distinct on (100) and (010). Dca]c = 2.17 g/cm3, Dmcas = 2.18(1) g/cm3. IR spectrum is'given. Günterblassite is biaxial (+), a = 1.488(2). p = 1.490(2), у = 1.493(2), 2f/ mcas = 80(5)°. Chemical composition (electron microprobe, mean of 7 point analyses, H2O determined by gas chromatography, wt %) is: Na2O 0.40, K2O 5.18, MgO 0.58, CaO 3.58, BaO 4.08, FeO 3.06, Al203 13.98, SiO2 52.94, H2O 15.2, total 98.99. The empirical formula is: Na0.15K1.24B0.30Ca0.72Mg0.16Fe2+0.48[Si9.91Al3.09O25.25(OH)3.75]·7.29H20. The crystal structure was studied for the single crystal, R = 0.049. Günterblassite is orthorhombic, space group Pnm21 unit-cell parameters are: a = 6.528(1), b = 6.970(1), c = 37.216 Å; V = 1693.3(4) A3; Z = 2. Günterblassite represents a new structural type. The most important specific feature of its structure is a block consisting of three single tetrahedral layers connected via common vertices. Thus, the new mineral can be considered as an intermediate species between phyllosilicates and tectosilicates. The strongest lines of its X-ray powder diffraction pattern [d, Å (I, %)] are: 6.523(100). 6.263(67), 3.244(49), 3.062(91), 2.996(66), 2.955(63), 2.763(60). The mineral was named in honor of Günter Blass (b. 1943), an amateur German mineralogist and a specialist in electron microprobe and X-ray diffraction analyses. Type specimens arc deposited in the Fersman Mineralogical Museum of the Russian Academy of Sciences, Moscow, with registration number 4107/1.