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Perettiit-(Y)

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Perettiit-(Y)

Stefan:
Hallo,

wieder mal habe ich ein Problem die Dichte die angegebenen wird mit den Werten die angegeben werden in Einklang zu bringen.

Die Empirische Formel und die angegebenen Gitterkonstanten sowie Z ergeben eine Dichte von 4.145 gcm3 und nicht 4.533gcm-3


--- Zitat ---Using the empirical formula, the density was estimated to be 4.533 g cm-3
--- Ende Zitat ---

Formel: Y2.06Ln0.53Zr0.02Th0.01Mn3.24Ca0.38Fe0.71Mg0.07Al0.11Li0.22Si1.95B7.44Be0.31O24
V = 759.71(5)Å3
Z = 2


Abstract:
The new mineral perettiite-(Y), end-member formula Y3+2Mn2+4Fe2+, from pegmatites in the region of Momeik, north of Mogok, Myanmar, occurs as yellow needles enclosed in phenakite crystals. The mineral was named after the mineralogist and gemologist Dr. Adolf Peretti. The empirical formula using LA-ICP-MS data (based on 24 O pfu) is Y2.06Ln0.53Zr0.02Th0.01Mn3.24Ca0.38Fe0.71Mg0.07Al0.11Li0.22 Si1.95B7.44Be0.31O24. Calculation of the H2O content using IR absorption data yields a maximum hydroxyl/water content equivalent to 0.1 wt.% H2O. The strongest lines in the powder pattern [d in Å, (Imeas.), (hkl)] are 4.63(52) (010), 4.08(28) (301, 103), 3.74(20) (210), 3.05(100) (113, 311, 303), 2.64(67) (410, 014), 2.54(60) (313), 2.12(23) (600, 006), 1.87(33) (420, 024), 1.84(52) (415, 323), 1.57(20) (026, 620), 144(25) (133, 331). The perettiite-(Y) crystals show a tetragonal X-ray diffraction pattern but the structure could only be solved as a 50/50 pseudo-merohedral orthorhombic twin with the a and c axes having the same length. The structure, refined to R1 = 0.017 (space group Pmna with a = 12.8252(5), b = 4.6187(2), c = 12.8252(5)Å, V = 759.71(5)Å3, Z = 2), is characterized by two eight-coordinated sites: one dominated by Y and lanthanoids (Ln) and the other by Mn2+ (with additional Ca2+ and Y3+). An octahedral site is occupied by (Fe2+, Mg) with additional Li+. These cation sites form an interlayer between two tetrahedral sheets of Si2B8O24 composition. Boron shows minor replacement by beryllium. Arrangement of 4-, 5- and 8-membered rings within (010) form the borosilicate tetrahedral layers. Perettiite-(Y) is brittle, with irregular fracture and (010) cleavage; the estimated Mohs hardness is ∼ 7. Using the empirical formula, the density was estimated to be 4.533 g cm-3. Perettiite-(Y) is biaxial, α = 1.82(1), γ = 1.84(1) (589 nm).
ROSA MICAELA DANISI; THOMAS ARMBRUSTER; EUGEN LIBOWITZKY; HAO A.O. WANG; DETLEF GÜNTHER; MARIKO NAGASHIMA; ERIC REUSSER; WILLY BIERI -  Y3+2Mn2+4Fe2+, a new mineral from Momeik, Myanmar  - European Journal of Mineralogy online: 26. August 2015

Stefan:
Ich habe Frau Rosa Micaela Dansi informiert.
Grüße Stefan

openpit:
Hallo Stefan,

eine Interessenfrage, welche vielleicht auch die Antwort auf das Problem gibt:
Welche M nimmt man denn für Ln an?

Danke und Glück Auf!
Micha

Stefan:
Genau da war der Fehler... Ln als Lanthanoide - hah da gibt es natürlich keine feste Atommasse, insofern fehlt hier natürlich die Masse. Unser Formelparser hatte da noch eine Lücke die nun geschlossen ist.

157,65 als Mittelwert werden wir nehmen.

Du bist der Held!
Grüße und Danke Stefan

Hier noch die Info von Fr. Dansi, die uns gerne unterstützt hat.


--- Zitat ---Calculations for <unnamed> mineral  Run on date: 4-December-2013

**************************************************
Calculations for mineral: perettite-(Y)  Run on date: 4-December-2013


CHEM (Formula Weight) calculations

Total Wt% =  99.56

Formula Weight = 1037.17

Constit     Data      Mole     Anion    Cation   Symbol    Number       k 
 Name       Wt %     Ratio     Ratio     Ratio            of Ions     Value
Li2O        0.32    0.0107    0.0107    0.0214     Li       0.223     0.307
BeO         0.75    0.0300    0.0300    0.0300     Be       0.312     0.240
MgO         0.27    0.0067    0.0067    0.0067     Mg       0.070     0.200
CaO         2.02    0.0360    0.0360    0.0360     Ca       0.375     0.210
MnO        22.06    0.3110    0.3110    0.3110    Mn2+      3.240     0.197
FeO         4.89    0.0681    0.0681    0.0681    Fe2+      0.709     0.188
B2O3       24.86    0.3571    1.0712    0.7142    B3+       7.440     0.215
Al2O3       0.56    0.0055    0.0165    0.0110     Al       0.114     0.207
Y2O3       22.32    0.0988    0.2965    0.1977     Y        2.059     0.170
Sm2O3       0.24    0.0007    0.0021    0.0014     Sm       0.014     0.130
Gd2O3       0.71    0.0020    0.0059    0.0039     Gd       0.041     0.123
Tb2O3       0.29    0.0008    0.0024    0.0016     Tb       0.017     0.119
Dy2O3       2.62    0.0070    0.0211    0.0140     Dy       0.146     0.115
Ho2O3       0.53    0.0014    0.0042    0.0028     Ho       0.029     0.112
Er2O3       1.78    0.0047    0.0140    0.0093     Er       0.097     0.108
Tm2O3       0.33    0.0009    0.0026    0.0017     Tm       0.018     0.104
Yb2O3       2.85    0.0072    0.0217    0.0145     Yb       0.151     0.101
Lu2O3       0.38    0.0010    0.0029    0.0019     Lu       0.020     0.097
SiO2       11.26    0.1874    0.3748    0.1874     Si       1.952     0.208
ZrO2        0.19    0.0015    0.0031    0.0015     Zr       0.016     0.211
ThO2        0.33    0.0012    0.0025    0.0012     Th       0.013     0.167

Total weight %     =   99.56
Total Anion Number =   24.00
Total Anion Ratio  =    2.3038
KC Value           =    0.189   or   0.1886
f-Factor           =   10.4176
Formula Weight     = 1037.17


Unit Cell Volume calculations

Crystal System : Orthorhombic
a = 12.8252      b = 4.6187      c = 12.8252
V = 759.7104      a:b:c =  2.7768 : 1 : 2.7768


Density calculations

D(calc) =    4.533 g/cm3
M       = 1037.174
V       =  759.710
Z       =    2.000
--- Ende Zitat ---

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