Birnessite Mineral Data

Birnessite Mineral Data +

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General Birnessite Information

Chemical Formula:

(Na,Ca,K)x(Mn++++,Mn+++)2O4·1.5(H2O)

Composition:

Molecular Weight = 215.71 gm

Potassium 1.81 % K 2.18 % K₂O

Sodium 3.20 % Na 4.31 % Na₂O

Calcium 1.86 % Ca 2.60 % CaO

Manganese 50.94 % Mn 36.59 % Mn₂O₃ / 40.30 % MnO₂

Hydrogen 1.40 % H 12.53 % H₂O

Oxygen 40.79 % O

______ ______

100.00 % 98.52 % = TOTAL OXIDE

Empirical Formula:

Na_0.3Ca_0.1K_0.1Mn⁴⁺Mn³⁺O₄·1.5(H₂O)

Environment:

Found as grains cementing gravel in a road cut 30 km N of Aberdeen. Major component of desert varnish. Deep sea Mn nodules.

IMA Status:

Valid Species (Pre-IMA) 1956

Locality:

Birness, Aberdeenshire, Scotland. Link to MinDat.org Location Data.

Name Origin:

Named after the locality.

Synonym:

ICSD 68916

PDF 23-1046

Birnessite Image

Images:

Birnessite

Comments: Gray birnessite. Very small crystals on massive material.
Location: Das Aufgekl?rte Gl?ck Mine, Hasserode, Wernigerode, Harz Mts, Saxony-Anhalt, Germany. Scale: Picture size 7 mm.
© Thomas Witzke / Abraxas-Verlag

Images:

Birnessite Buserite

Comments: Round, "rabbit pellets" of buserite which dehydrates to birnessite when dry. Image photographed through water which is needed to preserve this species.
Location: Aomori Springs, Oppu, Japan. Scale: Sphere size 7 mm.
© Dave Barthelmy

Birnessite Crystallography

Axial Ratios:

a:b:c =1.8154:1:2.574

Cell Dimensions:

a = 5.174, b = 2.85, c = 7.336, Z = 1; beta = 103.18° V = 105.33 Den(Calc)= 3.40

Crystal System:

Monoclinic - PrismaticH-M Symbol (2/m) Space Group: C 2/m

$Help on X Ray Diffraction:$ X Ray Diffraction:

By Intensity(I/I_o): 7.27(1), 1.41(0.7), 2.44(0.7),

Crystal Structure:

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Post J E , Veblen D R , American Mineralogist , 75 (1990) p.477-489, Crystal structure determinations of synthetic sodium, magnesium and potassium, birnessite using TEM and the Rietveld method, sample is Na-birn

View Additional jPOWD Structure files for Birnessite
[1] [2]

Physical Properties of Birnessite

Color:

Dark brown, Black.

Density:

Diaphaniety:

Subopaque

Habit:

Earthy - Dull, clay-like texture with no visible crystalline affinities, (e.g. howlite).

Habit:

Massive - Uniformly indistinguishable crystals forming large masses.

Hardness:

1.5 - Between Talc and Gypsum

Luster:

Sub Metallic

Optical Properties of Birnessite

Optical Data:

Biaxial (?), a=1.69, g=1.73, bire=0.0400

Calculated Properties of Birnessite

Electron Density:

r_electron=3.28 gm/cc
note: r_Birnessite=3.40 gm/cc.

Fermion Index

Fermion Index = 0.00022
Boson Index = 0.99978

Photoelectric:

PE_Birnessite= 13.58 barns/electron
U=PE_Birnessite x r_electron= 44.60 barns/cc.

Radioactivity:

GRapi = 25.26 (Gamma Ray American Petroleum Institute Units)

Estimated Radioactivity from Birnessite - barely detectable

Birnessite Classification

Dana Class:

7.5.3.1 (7)Multiple Oxides

(7.5)where A B X2

(7.5.3)Dana Group

7.5.3.1 Birnessite (Na,Ca,K)x(Mn,Mn)2O4·1.5(H2O) C 2/m 2/m

Strunz Class:

IV/F.11-30 IV - Oxides

IV/F - Hydroxides and oxidic hydrates, water-bearing oxides with layered structure

IV/F.11 - Jiansuiite - Birnessite series

IV/F.11-05 Jianshuiite (Mg,Mn)Mn3O7·3(H2O) R 3 or R 3 Trig

IV/F.11-10 Aurorite (Mn,Ag,Ca)Mn3O7·3(H2O) P1 1

IV/F.11-15 Ernienickelite NiMn3O7·3(H2O) R 3 or R 3 Trig

IV/F.11-20 Chalcophanite (Zn,Fe,Mn)Mn3O7·3(H2O) R 3 3

IV/F.11-25 Cianciulliite Mn(Mg,Mn)2Zn2(OH)10·2-4(H2O) C 2/m 2/m

IV/F.11-30 Birnessite (Na,Ca,K)x(Mn,Mn)2O4·1.5(H2O) C 2/m 2/m

Other Birnessite Information

References:

NAME( Dana8) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Enc. of Minerals,2nd ed.,1990)

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Birnessite

(Na,Ca,K)x(Mn++++,Mn+++)2O4·1.5(H2O)
Dana No: 7.5.3.1 Strunz No: IV/F.11-30
Locality:

Notes: