Brownmillerite Mineral Data

Brownmillerite Mineral Data +

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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.

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:

Brownmillerite Reinhardbraunsite

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 - DipyramidalH-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),

Crystal Structure:

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Redhammer G J , Tippelt G , Roth G , Amthauer G , American Mineralogist , 89 (2004) p.405-420, Structural variations in the brownmillerite series Ca2(Fe2-xAlx)O5:, Single-crystal X-ray diffraction at 25 deg C and high temperature, X-ray powder diffraction (25 C <= T <= 1000 C)

View Additional jPOWD Structure files for Brownmillerite
[1] [10] [11] [12] [13] [14] [15] [16] [17] [2] [3] [4] [5] [6] [7] [8] [9]

Physical Properties of Brownmillerite

Color:

Reddish brown.

Density:

3.76

Diaphaniety:

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

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:

r_electron=3.69 gm/cc
note: r_{Brownmillerite}=3.76 gm/cc.

Fermion Index

Fermion Index = 0.00504
Boson Index = 0.99496

Photoelectric:

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

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Brownmillerite is Not Radioactive

Brownmillerite Classification

Dana Class:

7.11.2.1 (7)Multiple Oxides

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

(7.11.2)Dana Group

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

7.11.2.2 Srebrodolskite Ca2Fe2O5 P nma 2/m 2/m 2/m

Strunz Class:

IV/A.07-10 IV - Oxides

IV/A - Oxides with metal : oxygen = 1:1 and 2:1 (M2O,MO)

IV/A.07 - Periclase Group, Brownmillerite - Mayenite series

IV/A.07-10 Brownmillerite Ca2(Al,Fe)2O5 Ibmm 2/m 2/m 2/m

IV/A.07-20 Srebrodolskite Ca2Fe2O5 P nma 2/m 2/m 2/m

IV/A.07-30 Mayenite Ca12Al14O33 I 43d 4 3m

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 -Google Images 5 -Google Scholar 6 -Handbook of Mineralogy (UofA) 7 -MinDAT 8 -MinMax(Deutsch) 9 -MinMax(English) 10 -Mineralienatlas (Deutsch) 11 -QUT Mineral Atlas 12 - WWW-MINCRYST 13 -École des Mines de Paris

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

Brownmillerite

Ca2(Al,Fe+++)2O5
Dana No: 7.11.2.1 Strunz No: IV/A.07-10
Locality:

Notes: