Brownmillerite Mineral Data

General Brownmillerite Information

Chemical Formula:

Ca2(Al,Fe+++)2O5

Composition:

Molecular Weight = 240.09 gm

Calcium 33.39 % Ca 46.71 % CaO

Aluminum 12.36 % Al 23.36 % Al₂O₃

Iron 20.93 % Fe 26.93 % FeO

Oxygen 33.32 % O

______ ______

100.00 % 97.00 % = TOTAL OXIDE

Empirical Formula:

Ca₂Al_1.1Fe²⁺_0.9O₅

Environment:

Thermally metamorphosed limestone blocks included in volcanic rocks.

IMA Status:

Approved IMA 1964

Locality:

Ettringer-Bellerberg volcano, near Mayen, Eifel district, Germay. Link to MinDat.org Location Data.

Name Origin:

Named for Lorrin Thomas Brownmiller (1902-), Chef chemist of the Alpha Portland Cement Company, Easton, Pennsylvania, USA.

Name Pronunciation:

Brownmillerite + Pronunciation

Synonym:

ICSD 9197

PDF 30-226

Brownmillerite Image

Images:

Brownmillerite

Comments: Brownish-orange masses of brownmillerite in skarn.
Location: Bellerberg, Ettringen, Eifel Mountains, Rheinland-Pfalz, Germany. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Images:

Reinhardbraunsite Brownmillerite

Comments: Pink crystalline reinhardbraunsite in brownmillerite.
Location: Near Bellerberg, Eifel, Rheinland-Pflaz, Germany. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Brownmillerite Crystallography

Axial Ratios:

a:b:c =0.3822:1:0.3698

Cell Dimensions:

a = 5.52, b = 14.44, c = 5.34, Z = 4; V = 425.64 Den(Calc)= 3.75

Crystal System:

Orthorhombic - Dipyramidal H-M Symbol (2/m 2/m 2/m) Space Group: Ibmm

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

By Intensity(I/I_o): 2.65(1), 2.78(0.5), 7.19(0.5),

Physical Properties of Brownmillerite

Color:

Reddish brown.

Density:

3.76

Diaphaneity:

Semitransparent

Habit:

Platy - Sheet forms (e.g. micas).

Habit:

Square - Occurs as square crystals in shape or outline.

Streak:

light brown

Optical Properties of Brownmillerite

Gladstone-Dale:

CI meas= -0.354 (Poor) - where the CI = (1-KPDmeas/KC)
CI calc= -0.358 (Poor) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2676,KPDmeas= 0.2668,KC= 0.1971
Ncalc = 1.74

Optical Data:

Biaxial (-), a=1.96, b=2.01, g=2.04, bire=0.0800, 2V(Calc)=72, 2V(Meas)=75.

Pleochroism (x):

yellow brown.

Pleochroism (y):

yellow brown.

Pleochroism (z):

dark brown.

Calculated Properties of Brownmillerite

Electron Density:

Bulk Density (Electron Density)=3.69 gm/cc
note: Specific Gravity of Brownmillerite =3.76 gm/cc.

Fermion Index:

Fermion Index = 0.0050487097
Boson Index = 0.9949512903

Photoelectric:

PE_{Brownmillerite}= 10.73 barns/electron
U=PE_{Brownmillerite} x rElectron Density= 39.57 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)
Brownmillerite is Not Radioactive

Brownmillerite Classification

Dana Class:

07.11.02.01 (07)Multiple Oxides

(07.11)as titano-oxides with [4] and [6] substitutions

(07.11.02)Dana Group

07.11.02.01 Brownmillerite Ca2(Al,Fe)2O5 Ibmm 2/m 2/m 2/m

07.11.02.02 Srebrodolskite Ca2Fe2O5 P nma 2/m 2/m 2/m

Strunz Class:

04.AC.10 04 - OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodate

04.A - Metal:Oxygen = 2.1 and 1:1

04.AC -M:O = 1:1 (and up to 1:1.25); with large cations (ï¿½ smaller ones)

04.AC.10 Brownmillerite Ca2(Al,Fe)2O5 Ibmm 2/m 2/m 2/m

04.AC.10 Srebrodolskite Ca2Fe2O5 P nma 2/m 2/m 2/m

Other Brownmillerite Information

References:

NAME( AntBidBlaNic2) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Enc. of Minerals,2nd ed.,1990)

See Also:

Links to other databases for Brownmillerite :
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
15 - WWW-MINCRYST

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

Brownmillerite

Ca2(Al,Fe+++)2O5
Dana No: 07.11.02.01 Strunz No: 04.AC.10
Locality:

Notes:

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