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Pyrolusite

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Formula:
MnO2
System:
Tetragonal
Colour:
Black or very dark grey.
Hardness:
2 - 6½
Member of:
Name:
Named in 1827 from the Greek for "fire" and "to wash," because it was used to remove brown and green tints in the making of glass.
Rutile Group.

Usually found as matte-black powdery to fibrous crusts, sometimes in botryoidal aggregates or columnar, more rarely as druzes of small prismatic to tabular, dark grey metallic crystals.
May be confused with some manganese oxides such as todorokite (fibrous variants) and manganite (tabular crystals).

NOTE: No valid pyrolusite dendrites are known. Supposed specimens of pyrolusite in dendritic form turn out to be other Mn-oxide species (e.g., minerals of the cryptomelane group, birnessite, nsutite, todorokite, etc.) upon being examined in the proper laboratory setting for characterizing these difficult to identify minerals; see Potter and Rossman (1979).



Classification of Pyrolusite

Approved, 'Grandfathered' (first described prior to 1959)
4.DB.05

4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
D : Metal: Oxygen = 1:2 and similar
B : With medium-sized cations; chains of edge-sharing octahedra
Dana 7th ed.:
4.4.1.4
4.4.1.4

4 : SIMPLE OXIDES
4 : AX2
7.18.3

7 : Oxides and Hydroxides
18 : Oxides of Mn

Occurrences of Pyrolusite

Physical Properties of Pyrolusite

Metallic, Dull, Earthy
Diaphaneity (Transparency):
Opaque
Colour:
Black or very dark grey.
Streak:
Black to bluish-black.
Hardness (Mohs):
2 - 6½
Hardness Data:
Measured
Comment:
6 to 6.5 when crystalline, 2 when massive.
Tenacity:
Brittle
Cleavage:
Perfect
Perfect on {110}.
Fracture:
Irregular/Uneven
Density:
5.04 - 5.08 g/cm3 (Measured)    5.189 g/cm3 (Calculated)

Crystallography of Pyrolusite

Crystal System:
Tetragonal
Class (H-M):
4/mmm (4/m 2/m 2/m) - Ditetragonal Dipyramidal
Space Group:
P42/mnm
Cell Parameters:
a = 4.4041(1) Å, c = 2.8765(1) Å
Ratio:
a:c = 1 : 0.653
Unit Cell Volume:
V 55.79 ų (Calculated from Unit Cell)
Z:
2
Morphology:
Crystals are uncommon, either long or short prismatic parallel to [001] or equant; more typically found as earthy powder or fibrous aggregates as crusts on rocks; sometimes as botryoidal aggregates, more rarely as druses of microscopic crystals.
Never found as dendrites despite old literature. [The obsolete term "polianite" was once used to refer to crystalline pyrolusite, which was assumed to be a different species than earthy to crusty pyrolusite.]
Twinning:
Twinning rare. Repeated twins with twin planes {031} and {032}. Polysynthetic twinning observed in polished sections.
X-Ray Powder Diffraction:
Image Loading

Radiation - Copper Kα
Data Set:
Data courtesy of RRUFF project at University of Arizona, used with permission.
X-Ray Powder Diffraction Data:
d-spacingIntensity
3.11(100)
2.41(60)
2.11(20)
1.62(60)
1.56(10)
1.306(20)
1.304(20)
1.000(10)
Comments:
Data given are for synthetic material.

Optical Data of Pyrolusite

Type:
Anisotropic
Anisotropism:
Strong, in yellows
Colour in reflected light:
Cream-white
Pleochroism:
Weak
Comments:
Very weak. Yellow to yellow gray.

Chemical Properties of Pyrolusite

Formula:
MnO2
Elements listed in formula:

Relationship of Pyrolusite to other Species

Member of:
Other Members of Group:
4.DB.05ArgutiteGeO2
4.DB.05CassiteriteSnO2
4.DB.05PlattneritePbO2
4.DB.05RutileTiO2
4.DB.05TripuhyiteFe3+Sb5+O4
4.DB.05TugarinoviteMoO2
4.DB.05Varlamoffite(Sn,Fe)(O,OH)2
4.DB.10ByströmiteMgSb25+O6
4.DB.10Tapiolite-(Fe)Fe2+Ta2O6
4.DB.10Tapiolite-(Mn)Mn2+Ta2O6
4.DB.10OrdoñeziteZnSb25+O6
4.DB.15bAkhtenskiteMnO2
4.DB.15cNsutiteMnx2+Mn4+1-xO2-2x(OH)2x
4.DB.15aParamontroseiteVO2
4.DB.15aRamsdelliteMn4+O2
4.DB.20ScrutinyitePbO2
4.DB.25Ishikawaite(U,Fe,Y)NbO4
4.DB.25Ixiolite(Ta,Mn,Nb)O2
4.DB.25Samarskite-(Y)(Y,Ce,U,Fe,Nb)(Nb,Ta,Ti)O4
4.DB.25SrilankiteTi2ZrO6
4.DB.25Yttrocolumbite-(Y)(Y,U,Fe2+)(Nb,Ta)O4
4.DB.25Calciosamarskite(Ca,Fe,Y)(Nb,Ta,Ti)O4
4.DB.25Samarskite-(Yb)YbNbO4
4.DB.30FerberiteFe2+WO4
4.DB.30HübneriteMn2+WO4
4.DB.30SanmartiniteZnWO4
4.DB.30KrasnoselskiteCoWO4
4.DB.30HeftetjerniteScTaO4
4.DB.30HuanzalaiteMgWO4
4.DB.35Columbite-(Fe)Fe2+Nb2O6
4.DB.35Tantalite-(Fe)Fe2+Ta2O6
4.DB.35Columbite-(Mn)Mn2+Nb2O6
4.DB.35Tantalite-(Mn)Mn2+Ta2O6
4.DB.35Columbite-(Mg)MgNb2O6
4.DB.35QitianlingiteFe22+Nb2W6+O10
4.DB.35Magnocolumbite(Mg,Fe,Mn)(Nb,Ta)2O6
4.DB.35Tantalite-(Mg)MgTa2O6
4.DB.40FerrowodginiteFe2+Sn4+Ta2O8
4.DB.40LithiotantiteLiTa3O8
4.DB.40LithiowodginiteLiTa3O8
4.DB.40TitanowodginiteMn2+TiTa2O8
4.DB.40WodginiteMn2+Sn4+Ta2O8
4.DB.40FerrotitanowodginiteFe2+TiTa2O8
4.DB.40WolframowodginiteMn(Mn,Sn,Fe,Ta)(W,Ta,Nb)2O8
4.DB.45TivaniteTiV3+O3(OH)
4.DB.50Carmichaelite(Ti,Cr,Fe)(O,OH)2
4.DB.55AlumotantiteAlTaO4
4.DB.60BiehliteSb23+MoO6
7.18.1ManganositeMn2+O
7.18.2HausmanniteMn2+Mn23+O4
7.18.4RamsdelliteMn4+O2
7.18.5AkhtenskiteMnO2
7.18.6FeitknechtiteMn3+O(OH)
7.18.7ManganiteMn3+O(OH)
7.18.8GroutiteMn3+O(OH)
7.18.9NsutiteMnx2+Mn4+1-xO2-2x(OH)2x
7.18.10PyrochroiteMn2+(OH)2
7.18.11Birnessite(Na,Ca,K)0.6(Mn4+,Mn3+)2O4 · 1.5H2O
7.18.12Aurorite(Mn2+,Ag,Ca)Mn34+O7 · 3H2O
7.18.13CianciulliiteMg2Mn2+Zn2(OH)10 · 2-4H2O

Other Names for Pyrolusite

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.

References for Pyrolusite

Reference List:
Dana and Penfield (1888) American Journal of Science: 35: 243.

St. John (1923) Physical Reviews: 21: 389.

Ferrari (1926) Acc. Linc., Att.: 3: 224.

Vaux, G., Bennett, M.H. (1937) X-Ray Studies on Pyrolusite (Including Polianite) and Psilomelane. Mineralogical Magazine: 24: 521.

Palache, C., Berman, H., Frondel, C. (1944) The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana Yale University 1837-1892, Volume I: Elements, Sulfides, Sulfosalts, Oxides. John Wiley and Sons, Inc., New York. 7th edition, revised and enlarged: 562-566.

Neues Jahrbuch für Mineralogie, Monatshefte (1974): 8: 371-384.

Potter, R., Rossman, G. (1979) The Tetravalent Manganese Oxides: Identification, hydration and Structural Relationships by Infrared Spectroscopy. American Mineralogist: 64: 1199-1218.

Gaines, R.V., Skinner, H.C.W., Foord, E.E., Mason, B., Rosenzweig, A., King, V.T. (1997) Dana's New Mineralogy: The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana: 238.

Kohler, T., Armbruster, T., Libowitzky, E. (1997) Hydrogen bonding and Jahn-Teller distortion in groutite, α-MnOOH, and manganite, γ-MnOOH, and their relations to the manganese dioxides ramsdellite and pyrolusite. Journal of Solid State Chemistry: 133: 486-500.

Internet Links for Pyrolusite

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http://www.mindat.org/min-3318.html
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Specimens:
The following Pyrolusite specimens are currently listed for sale on minfind.com.

Localities for Pyrolusite

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