Mineralogy Database

Mullite Mineral Data

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General Mullite Information

Help on Chemical  Formula: Chemical Formula: Al(4+2x)Si(2-2x)O(10-x) where x =0.17 to 0.59
Help on Composition: Composition: Molecular Weight = 319.54 gm
   Aluminum  38.00 %  Al   71.79 % Al2O3
   Silicon   13.18 %  Si   28.21 % SiO2
   Oxygen    48.82 %  O
            ______        ______ 
            100.00 %      100.00 % = TOTAL OXIDE
Help on Empirical Formula: Empirical Formula: Al4.5Si1.5O9.75
Help on Environment: Environment: Remelted Tertiary-aged clays.
Help on IMA Status: IMA Status: Valid Species (Pre-IMA) 1924
Help on Locality: Locality: Isle of Mull, Scotland, England. Link to MinDat.org Location Data.
Help on Name Origin: Name Origin: Named after its locality.
Help on Name Pronunciation: Name Pronunciation: Mullite Say MULLITE

Mullite Image

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Comments: Opaque white mullite masses with mica.
Location: Nijar, Almeria, Andalucia, Spain. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

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Comments: Surface of a kaolinite stratum altered to white mullite by a prehistoric coal-seam-fire..
Location: Mt. Wingen (Burning Mountain), NSW, Australia. Scale: Picture size 6x4 cm.
© Dave Barthelmy

Mullite Crystallography

Help on Axial Ratios: Axial Ratios: a:b:c =0.9865:1:0.3757
Help on Cell Dimensions: Cell Dimensions: a = 7.5785, b = 7.6817, c = 2.8864, Z = 1; V = 168.03 Den(Calc)= 3.16
Help on Crystal System: Crystal System: Orthorhombic - Dipyramidal H-M Symbol (2/m 2/m 2/m) Space Group: Pbam
Help on X Ray Diffraction: X Ray Diffraction: By Intensity(I/Io): 3.39(1), 3.428(0.95), 2.206(0.6),

Physical Properties of Mullite

Help on Cleavage: Cleavage: {010} Good
Help on Color: Color: Colorless, Violet, Yellow, White, Light pink.
Help on Density: Density: 3 - 3.1, Average = 3.05
Help on Diaphaneity: Diaphaneity: Transparent to translucent
Help on Fracture: Fracture: Brittle - Generally displayed by glasses and most non-metallic minerals.
Help on Habit: Habit: Crystalline - Fine - Occurs as well-formed fine sized crystals.
Help on Habit: Habit: Prismatic - Crystals Shaped like Slender Prisms (e.g. tourmaline).
Help on Hardness: Hardness: 6-7 - Orthoclase-Quartz
Help on Luminescence: Luminescence: Non-fluorescent.
Help on Luster: Luster: Vitreous (Glassy)
Help on Streak: Streak: white

Optical Properties of Mullite

Help on Gladstone-Dale: Gladstone-Dale: CI meas= -0.035 (Excellent) - where the CI = (1-KPDmeas/KC)
CI calc= 0.001 (Superior) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2071,KPDmeas= 0.2146,KC= 0.2073
Ncalc = 1.62 - 1.66
Help on Optical Data: Optical Data: Biaxial (+), a=1.642-1.653, b=1.644-1.655, g=1.654-1.679, bire=0.0120-0.0260, 2V(Calc)=34-50, 2V(Meas)=20-50. Dispersion r > v.
Help on Pleochroism (x): Pleochroism (x): colorless or colorless.
Help on Pleochroism (y): Pleochroism (y): colorless or colorless.

Calculated Properties of Mullite

Help on Electron Density: Electron Density: Bulk Density (Electron Density)=3.12 gm/cc
note: Specific Gravity of Mullite =3.16 gm/cc.
Help on Fermion Index: Fermion Index: Fermion Index = 0.0063912836
Boson Index = 0.9936087164
Help on Photoelectric: Photoelectric: PEMullite = 1.62 barns/electron
U=PEMullite x rElectron Density= 5.04 barns/cc.
Help on Radioactivity: Radioactivity: GRapi = 0 (Gamma Ray American Petroleum Institute Units)
Mullite is Not Radioactive

Mullite Classification

Help on  Dana Class: Dana Class: 52.02.02a.02 (52)Nesosilicate Insular SiO4 Groups and O, OH, F, and H2O
  (52.02)with cations in [4] and >[4] coordination
  (52.02.02a)Al2SiO5 (Sillimanite subgroup)
52.02.02a.01 Sillimanite Al2SiO5=Al[6]Al[4]OSiO4 P nma 2/m 2/m 2/m
52.02.02a.02 Mullite Al(42x)Si(2-2x)O(10-x)wherex=0.17to0.59 Pbam 2/m 2/m 2/m
52.02.02a.03 Boromullite! Al4.5SiB0.5O9.5 C mc21 mm2
Help on  Strunz Class: Strunz Class: 09.AF.20 09 - SILICATES (Germanates)
  09.A - Nesosilicates
  09.AF -Nesosilicates with additional anions;
09.AF.20 Mullite Al(42x)Si(2-2x)O(10-x)wherex=0.17to0.59 Pbam 2/m 2/m 2/m

Other Mullite Information

Help on See Also: See Also: Links to other databases for Mullite :
1 - Am. Min. Crystal Structure Database
2 - Athena
3 - EUROmin Project
4 - Ecole des Mines de Paris
5 - GeoScienceWorld
6 - Google Images
7 - Google Scholar
8 - Handbook of Mineralogy (MinSocAm)
9 - Handbook of Mineralogy (UofA)
10 - MinDAT
11 - Mineralienatlas (Deutsch)
12 - Online Mineral Museum
13 - QUT Mineral Atlas
14 - Ruff.Info

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Print or Cut-and-Paste your Mullite Specimen Label here :


Al(4+2x)Si(2-2x)O(10-x) where x =0.17 to 0.59
Dana No: 52.02.02a.02 Strunz No: 09.AF.20





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