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(x ~ 0.4)
Colourless, white, ...
6 - 7
Named after the discovery locality, the Isle of Mull, Scotland.
Synthetic mullite is well-known as a high-performance ceramic.

Compare 'meta-kaolinite', 'pseudomullite', and 'silicon spinel' - a synthetic phases being intermediate product of mullite formation from kaolinite.

Classification of Mullite

Approved, 'Grandfathered' (first described prior to 1959)
First Published:

9 : SILICATES (Germanates)
A : Nesosilicates
F : Nesosilicates with additional anions; cations in [4], [5] and/or only [6] coordination

52 : NESOSILICATES Insular SiO4 Groups and O,OH,F,H2O
2 : Insular SiO4 Groups and O, OH, F, and H2O with cations in [4] and >[4] coordination

15 : Silicates of Aluminum

Physical Properties of Mullite

Diaphaneity (Transparency):
Transparent, Translucent
Colourless, white, yellow, pink, red, gray
Hardness (Mohs):
6 - 7
Distinct on {010}
3.11 - 3.26 g/cm3 (Measured)    3.17 g/cm3 (Calculated)

Optical Data of Mullite

Biaxial (+)
RI values:
nα = 1.642 - 1.653 nβ = 1.644 - 1.655 nγ = 1.654 - 1.679
Measured: 20° to 50°, Calculated: 34° to 50°
Max Birefringence:
δ = 0.012 - 0.026
Image shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:
r > v
X=Y= colorless
Z= rose-pink

Chemical Properties of Mullite


(x ~ 0.4)
IMA Formula:
Al4+2xSi2-2xO10-x (x~0.4)
Elements listed in formula:
Common Impurities:

Crystallography of Mullite

Crystal System:
Class (H-M):
mmm (2/m 2/m 2/m) - Dipyramidal
Space Group:
Cell Parameters:
a = 7.5785(6) Å, b = 7.6817(7) Å, c = 2.8864(3) Å
a:b:c = 0.987 : 1 : 0.376
Unit Cell Volume:
V 168.03 ų (Calculated from Unit Cell)
Crystals prismatic to acicular.
On synthetic material. Structure is incommensurately modulated.
X-Ray Powder Diffraction Data:
5.39 (50)
3.390 (100)
3.428 (95)
2.694 (40)
2.542 (50)
2.206 (60)
1.5242 (35)
For synthetic material.

Type Occurrence of Mullite

Relationship of Mullite to other Species

9.AF.50Unnamed (Ca-analogue of Humite)Ca7(SiO4)4F2
15.11Allophane(Al2O3)(SiO2)1.3-2 · 2.5-3H2O

Other Names for Mullite

Name in Other Languages:

Other Information

Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

Mullite in petrology

Accessory component of (items highlighted in red)

References for Mullite

Reference List:
Bowen, N.L., Greig, J.W., Zies, E.G. (1924) Mullite, a silicate of alumina. Journal of the Washington Academy of Sciences: 14: 183-191 .

Foshag, W.F. (1924) New minerals: new species. American Mineralogist: 9: 211-212.

Agrell, S.O., Smith, J.V. (1957) X-ray crystallography of mullite, sillimanite and praguite. Acta Crystallographica: 10: 761-761.

Brindley, G.W. and Nakahira, M. (1959) The kaolinite-mullite reaction series: I, Survey of outstanding problems. II, Metakaolin. III, The high-temperature phases. Journal of the American Ceramic Society: 42: 311-324.

Durovic, S. (1962) A statistical model for the crystal structure of mullite. Soviet Physics - Crystallography: 7: 271-278.

Ernst, W.G., Calvert, S.E. (1969) An experimental study of the recrystallization of porcelanite and its bearing on the origin of some bedded cherts: American Journal of Science: 267A: 114-133.

Cameron, W.E. (1977) Mullite: a substituted alumina. American Mineralogist: 62: 747-755.

Leonard, A.J. (1977) Structural analysis of the transition phases in the kaolinite-mullite thermal sequence. Journal of the American Ceramic Society: 60: 37-43.

Angel, R.J., Prewitt, C.T. (1986) Crystal structure of mullite: A re-examination of the average structure. American Mineralogist: 71: 1476-1482.

Srikrisna, K., Thomas, G., Martinez, R., Corral, M.P., de Aza, S., and Moya, J.S. (1990) Kaolinite-mullite reaction series: a TEM study. Journal of Materials Science: 25: 607-612.

Angel, R.J., McMullan, R.K., Prewitt, C.T. (1991) Substructure and superstructure of mullite by neutron diffraction. American Mineralogist: 76: 332-342.

Niven, M.L., Waters, D.J., Moore, J.M. (1991) The crystal structure of werdingite, (Mg,Fe)2Al12(Al,Fe)2Si4(B,Al)4O37, and its relationship to sillimanite, mullite, and grandidierite. American Mineralogist: 76: 246-256.

Kahn-Harari, A., Abolhassani, S., Michel, D., Mazerolles, L., Portier, R., Perez-Ramirez, J.G. (1991) Observation of ordering in silicon and germanium mullites. Journal of Solid State Chemistry: 90: 234-248.

Querol, X., Fernandez Turiel, J.L., Lopez Soler, A. (1994): The behaviour of mineral matter during combustion of Spanish subbituminous and brown coals. Mineralogical Magazine: 58: 119-133

Lee, S., Kim, Y.J., Moon, H.S. (1999) Phase transformation sequence from kaolinite to mullite investigated by an energy-filtering transmission electron microscope. Journal of the American Ceramic Society: 82: 2841-2848.

Voll, D., Lengauer, C., Beran, A., Schneider, H. (2001) Infrared band assignment and structural refinement of Al-Si, Al-Ge, and Ga-Ge mullites. European Journal of Mineralogy: 13: 591-604.

Voll, D., Angerer, P., Beran, A., and Schneider, H. (2002) A new assignment of IR vibrational modes in mullite. Vibrational Spectroscopy: 30: 237-243.

Rodriguez-Navarro, C., Cultrone, G., Sanchez-Navas, A., and Sbastian, E. (2003) TEM study of mullite growth after muscovite breakdown. American Mineralogist: 88: 713-724.

Birkenstock, J., Petrícek, V., Pedersen, B., Schneider, H., Fischer, R. X. (2015) The modulated average structure of mullite. Acta Crystallogr: B71: 358-368.

Fischer, R.X., Tikhonova, V., Birkenstock, J., Fischer, L.A., Herrmann, K., Mengel, K., Schneider, H. (2015) A new mineral from the Bellerberg, Eifel, Germany, intermediate between mullite and sillimanite. American Mineralogist: 100: 1493-1501.

Bost, N., Duraipandian, S., Guimbretière, G., Poirier, J. (2016) Raman spectra of synthetic and natural mullite. Vibrational Spectroscopy: 82: 50-52.

Internet Links for Mullite URL:
Please feel free to link to this page.

Localities for Mullite

This map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
(TL) indicates type locality for a valid mineral species. (FRL) indicates first recorded locality for everything else. ? indicates mineral may be doubtful at this locality. All other localities listed without reference should be considered as uncertain and unproven until references can be found.
  • Tasmania
    • Huon Valley municipality
      • Huon-Channel region
        • Weld River district
R Bottrill in prep
  • Burgenland
    • Oberpullendorf
      • Kobersdorf
        • Pauliberg
U. Kolitsch, W. Postl, H.-P. Bojar and W. Trattner (2009): Die Mineralvorkommen im Basalt des Pauliberges. In: Autorenkollektiv (Red. M. A. Götzinger und P. Huber) (2009): Die Mineralien des Burgenlandes - Geologie, Mineralogie und mineralische Rohstoffe. – Wissenschaftliche Arbeiten aus dem Burgenland, Band 126, Amt der Burgenländischen Landesregierung, Abteilung 7 - Landesmuseum, Eisenstadt, 83-99.
  • Styria
    • Bad Radkersburg
      • Klöch
"Aus der Tiefe der Vulkane", Fritz-Jandl-Postl (2011)
  • Gansu Province
    • Jiuquan Prefecture
      • Subei Co.
        • Gongpoquan ore field
Gansu Province Metallurgical and Geological Exploration Team No. 4 (1978): Geology and Prospecting 14(8), 20-23
Guangce Zeng, Baoming Pan, and Shangyue Shen (1993): Acta Mineralogica Sinica 13(1), 84-86
  • Shanxi Province
    • Yangquan Prefecture
      • Kuang District
Querol, X.; Izquierdo, M.; Monfort, E.; Alvarez, E.; Font, O.; Moreno, T.; Alastuey, A.; Zhuang, X.; Lu, W.; Wang, Y. (2008): International Journal of Coal Geology 75, 93-104
Czech Republic
  • Bohemia (Böhmen; Boehmen)
    • Central Bohemia Region
Zacek, V., Oplustil, S., Mayova, A. & Meyer, F. R. (1995): Die Mineralien von Kladno in Mittelböhmen, Tschechische Republik. Mineralien-Welt 6 (1), 13-30 (in German).
        • Libušin
David Parfitt collection; Hyrsl J., Korbel P.; Tschechien & Slowakei, Mineralien und Fundstellen. Bode Verlag, 2008. Page 268-273
    • Hradec Králové Region
      • Trutnov (Trautenau)
        • Radvanice
Jirásek, J.: Thermal Changes of the Rocks in the Dump Pile of the Kateřina Colliery in Radvanice (Eastern Bohemia). Ostrava: VSB – Technical University of Ostrava, Institute of Geological Engineering - 541, 2001. 69 p.
    • Ústí Region
      • Most
Ferry FEDIUK, Anna LANGROVÁ and Karel MELKA. 2003. "North Bohemian Porcellanites and their Mineral Composition: the Case of the Dobrčice Quarry, the Most Basin" GeoLines 15, p. 35-43. PDF:
  • Matruh Governorate
    • East Uweinat Desert
Gian Paolo Sighinolfi, Chiara Elmi, Romano Serra, and Gabriele Contini (2014): High density silica phases as evidence of small-scale hypervelocity impacts: the Gebel Kamil Crater (Egypt). Periodico di Mineralogia 83, 299-312.
  • Auvergne-Rhône-Alpes
    • Haute-Loire
      • Le Puy-en-Velay
        • Espaly-Saint-Marcel
Barrier D, Pourtier G, Médard P (2004) Minéralogie du mont Denise (Haute-Loire). Le Cahier des Micromonteurs 83: 3-11.
  • Bavaria
    • Franconia
      • Fichtelgebirge
        • Marktredwitz
          • Pechbrunn
Weiss: "Mineralfundstellen, Deutschland West", 1990
    • Upper Palatinate
      • Kemnath
        • Waldeck
Pöllmann et al. (2007): Aufschluss 58, 227-233.
      • Wiesau
        • Triebendorf
Weiss: "Mineralfundstellen, Deutschland West", 1990
  • Hesse
    • Cornberg
Müller, G. (1967): Contributions to Mineralogy and Petrology 14, 176-189.
  • Lower Saxony
    • Osnabrück
      • Georgsmarienhütte
Schnorrer, G., Stahlmann, W., Mollenkamp, A. (2001): Sekundärmineralisation in den Hochofenschlacken des Hüttenwerkes in Georgsmarienhütte, heutige Georgsmarienhütte GmbH. Aufschluss 52, 99-108.
  • North Rhine-Westphalia
    • Aachen
      • Alsdorf
T. Witzke, F. de Wit, U. Kolitsch and G. Blaß (2015): Mineralogy of the Burning Anna I Coal Mine Dump, Alsdorf, Germany. Chapter 7, 203-240; in: Stracher, G. B., Prakash, A. and Sokol, E. V.: Coal and Peat Fires: A Global Perspective, Volume 3: Case Studies - Coal Fires, Elsevier.
  • Rhineland-Palatinate
    • Eifel
      • Andernach
        • Nickenich
Hentschel, G., Die Mineralien der Eifelvulkane, Weise Verlag München, 1983
Hentschel, G., Die Mineralien der Eifelvulkane, Weise Verlag München, 1983
      • Daun
        • Oberstadtfeld
Leu, K., Der Vulkanabbau "Auf´m Kopp" bei Oberstadtfeld in der Westeifel, Lapis 2/1995
        • Üdersdorf
Schäfer, H., Die Mineralien der Einschlüsse und Auswürflinge in den Schlacken des Emmelberges bei Üdersdorf / Eifel, Der Aufschluss 30, 273-282, 1979
Guth, G., Interessante Neufunde für den Basaltbruch Liley (Löley) bei Üdersdorf in der Westeifel Mineralien-Welt 2/2000
      • Gerolstein
        • Roth
Blaß, G. & Schüller, W. (2012): Der Rother Kopf in der Vulkaneifel. Lapis, 37 (3), 20-29.
      • Kelberg
        • Drees
Schüller, W., Die Mineralien des Niveligsberges bei Drees in der Eifel, Der Aufschluß SB 33, 1990
      • Laach lake volcanic complex
        • Kruft
Blass, G.; Graf, H.W., Neufunde von bekannten Fundorten (X), Mineralien-Welt 5/2, 43, 1994
        • Mendig
          • Niedermendig
Blass, G.; Graf, H.W., Neufunde von bekannten Fundorten (X), Mineralien-Welt 5/2, 43, 1994
Blass, G.; Graf, H.W., Neufunde von bekannten Fundorten (X), Mineralien-Welt 5/2, 43, 1994
            • Wingertsberg
Blass, G.; Graf, H.W., Neufunde von bekannten Fundorten (X), Mineralien-Welt 5/2, 43, 1994
      • Mayen
        • Ettringen
          • Bellerberg volcano
Hentschel, G., Neufunde seltener Minerale im Laacher Vulkangebiet, Aufschluß 28, 129-133, 1977
      • Mendig
        • Bell
Hentschel, G., Die Mineralien der Eifelvulkane, Weise Verlag München, 1983
      • Niederzissen
        • Burgbrohl
Hentschel, G., Die Mineralien der Eifelvulkane, Weise Verlag München, 1983
      • Polch
        • Ochtendung
Lapis 1988(7+8), 70-72
  • Saxony
    • Zwickau
      • Oelsnitz
T. Witzke (1996): Die Minerale der brennenden Halde der Steinkohlengrube "Deutschland-schacht" in Oelsnitz bei Zwickau.- Aufschluss 47, 41-48
  • Thuringia
    • Gera
      • Ronneburg U deposit
T. Witzke & F. Rüger: Lapis 1998(7/8), 26-64
  • Vas Co.
    • Kemeneshát
      • Celldömölk
Szakáll & Gatter. Hun. Min. Spec., 1993
  • Odisha (Orissa)
    • Cuttack District
Mallick, B., Rautray, T. R., Nayak, P. K., Vijayan, V., Singh, P., Behera, R. C., ... & Choudhury, R. K. (2005, March). Characterisation of hot material erupted from Mahanadi riverbank using EDXRF and XRD techniques. In INDIAN JOURNAL OF PHYSICS AND PROCEEDINGS OF THE INDIAN ASSOCIATION FOR THE CULTIVATION OF SCIENCE-NEW SERIES- (Vol. 79, No. 3, p. 293). NOT KNOWN.
  • Campania
    • Naples Province
      • Somma-Vesuvius Complex
        • Monte Somma
          • Ercolano
Russo, M. & Preite, D. (2011): Nuove specie minerali al Monte Somma: IV. Mullite. Micro, 2/2011, 60-61
  • Latium
    • Viterbo Province
      • Piansano
Burli, M., Nizi, L., Pucci, R., Signoretti, E (2010): Mullite et Cordierite nella cava di Cellere (VT), Il Cercapietre , 1-2 / 2010, pp. 41-48
  • Sardinia
    • Oristano Province
      • Mt. Arci
        • Marrubiu
Bortolozi G. (1986) - Mullite e Pseudobrookite del M. Arci (Or) - Riv. Mineral. Ital. , Milano, Fasc. 3, pag. 136
Bortolozi G. (1986) - Mullite e Pseudobrookite del M. Arci (Or) - Riv. Mineral. Ital. , Milano, Fasc. 3, pag. 136
  • Honshu Island
    • Chubu region
      • Nagano prefecture
Matsubara et al (1998) Ganko-Gakkai Kou'en-Youshi, 34.
  • Limburg
    • Kerkrade
New Zealand
  • North Island
    • Bay of Plenty
      • Rotorua
        • Mt Ngongotaha
Martin Stolworthy Collection
    • Waikato
      • Taupo
        • Atiamuri
Personal collection of Rod Martin
        • Lake Taupo
Collection of Rod Martin
Thornton, J. (Ed.), The Micro-Scope, No. 41, February 2002
Collection of RJ Martin; ko jansen
Essence of Microscope, 2004
  • Lower Silesia (Dolnośląskie)
    • Kłodzko District
      • Nowa Ruda (Neurode)
        • Słupiec Mine (John Mine)
Ciesielczukk, J., Kruszewski, Ł., Fabiańska, M.J., Misz-Kennan, M., Kowalski, A., Mysza, B., 2014: Efflorescences and gas composition emitted from the burning coal-waste dump in Słupiec, Lower Silesian Coal Basin, Poland. Proceedings of the International Symposium CEMC 2014, Skalský Dvůr, April 23-26th, 26-27
  • Upper Silesia (Śląskie)
    • Upper Silesian Coal Basin
      • Katowice area
        • Łaziska
Lukasz Kruszewski 2005: Minerals arising in cause of underground fires of "Skalny" coal mine dump in Laziska, Upper Silesia.Mag. Thesis (unpublished)
  • Eastern-Siberian Region
    • Krasnoyarsk Territory (Krasnoyarsk Kray; Krasnoyarskii Krai)
      • Anabarskii massif
        • Popigai river
Masaitis, V. L. (1998). Popigai crater: Origin and distribution of diamond‐bearing impactites. Meteoritics & Planetary Science, 33(2), 349-359.
  • Urals Region
    • Southern Urals
      • Chelyabinsk Oblast'
Cesnokov, B., Kotrly, M. and Nisanbajev, T. (1998): Brennende Abraumhalden und Aufschlüsse im Tscheljabinsker Kohlenbecken - eine reiche Mineralienküche. Mineralien-Welt, 9 (3), 54-63 (in German).
No reference listed
  • Košice Region
    • Michalovce Co.
Bacsó,Z.,Ďuďa,R.,1988: Metalogenéza a rudné formácie rudného poľa Remetské Hámre. Min.Slovaca,Bratislava, 3, 193-220p
    • Sobrance Co.
      • Remetské Hámre
[European Journal of Mineralogy 13:177-186]
South Africa
  • Free State Province
    • Lejweleputswa District
      • Boshof
Mathias, M., Siebert, J.C., and Rickwood, P.C. (1970): Contributions to Mineralogy and Petrology 26, 75-123.
  • Andalusia
    • Almería
Robert A. Jenkins
  • Aragón
    • Teruel
      • Montalbán
- Calvo, M. (2008): Minerales de Aragón. Prames, Zaragoza. 463 pags.
      • Utrillas
-- Calvo, M. (2008): Minerales de Aragón. Prames, Zaragoza. 463 pags.
  • Viloyati Sogd (Viloyati Sughd; Viloyati Khodzhent; Viloyati Leninabad)
    • Zeravshan Range
      • Yagnob River
Sharygin, V.V., Sokol, E.V. and Belakovskii, D.I. (2009): Fayalite-sekaninaite paralava from the Ravat coal fire (central Tajikistan). Russian Geology and Geophysics 50, 703-721.
Nasdala, L., & Pekov, I. V. (1993). Ravatite, C14HIO, a new organic mineral species from Ravat, Tadzhikistan. Eur. J. Mineral, 5, 699-705.
  • Scotland
    • Strathclyde
      • Isle of Mull
No reference listed
BMS Database
N L. Bowen, J W. Greig and E G. Zies. Mullite, a silicate of alumina. Jour Wash. Acad. Sci., 14, 183, 1924.
BMS Database; Am Min 50:1982-2022
  • Idaho
    • Shoshone Co.
      • Goat Mountain District
U.S. Geological Survey, 2005, Mineral Resources Data System: U.S. Geological Survey, Reston, Virginia.
  • Illinois
    • Vermilion Co.
      • Danville
        • Hegeler
Piatak, N. M. & Seal, R. R., II (2010): Mineralogy and the release of trace elements from slag from the Hegeler Zinc smelter, Illinois (USA). Applied Geochemistry, 25, 302-320
  • New Jersey
    • Middlesex Co.
AmMin 10:152-155
  • Wyoming
    • Campbell Co.
      • Reno Junction
Gunnar Farber
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