Congolite Mineral Data

Congolite Mineral Data

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General Congolite Information

Chemical Formula:

(Fe++,Mg,Mn)3B7O13Cl

Composition:

Molecular Weight = 458.00 gm

Magnesium 4.78 % Mg 7.92 % MgO

Manganese 3.60 % Mn 4.65 % MnO

Iron 21.95 % Fe 28.24 % FeO

Boron 16.52 % B 53.20 % B₂O₃

Chlorine 7.74 % Cl 7.74 % Cl

- % Cl -1.75 % -O=Cl₂

Oxygen 45.41 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

Fe²⁺_1.8Mg_0.9Mn²⁺_0.3B₇O₁₃Cl

IMA Status:

Approved IMA 1972

Locality:

Link to MinDat.org Location Data.

Synonym:

ICSD 60504

PDF 25-2

Congolite Image

Images:

Congolite

Comments: Pearly crystalline grains of congolite.
Location: Brazzaville, Pool, Congo. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Congolite Crystallography

Axial Ratios:

a:c = 1:2.44175

Cell Dimensions:

a = 8.6225, c = 21.054, Z = 6; V = 1,355.60 Den(Calc)= 3.37

Crystal System:

Trigonal - Ditrigonal PyramidalH-M Symbol (3m) Space Group: R 3c

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

By Intensity(I/I_o): 2.725(1), 3.05(0.8), 2.061(0.75),

Crystal Structure:

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Dowty E , Clark J R , Zeitschrift fur Kristallographie , 138 (1973) p.64-99, Crystal-structure refinements for orthorhombic boracite,, Mg3B7O13Cl, and a trigonal, iron-rich analogue, Locality: Bischofferode, Thuringen, Germany

Physical Properties of Congolite

Color:

Light red.

Density:

3.58

Diaphaniety:

Transparent

Hardness:

6.5-7.5

Luster:

Vitreous (Glassy)

Optical Properties of Congolite

Gladstone-Dale:

CI meas= 0.043 (Good) - where the CI = (1-KPDmeas/KC)
CI calc= -0.016 (Superior) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2205,KPDmeas= 0.2075,KC= 0.2169

Optical Data:

Uniaxial (-), e=1.731, w=1.755, bire=0.0240.

Calculated Properties of Congolite

Electron Density:

r_electron=3.25 gm/cc
note: r_Congolite=3.37 gm/cc.

Fermion Index

Fermion Index = 0.04252
Boson Index = 0.95748

Photoelectric:

PE_Congolite= 8.32 barns/electron
U=PE_Congolite x r_electron= 27.06 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Congolite is Not Radioactive

Congolite Classification

Dana Class:

25.6.2.1 (25)Anhydrous Borates Containing Hydroxyl or Halogen

(25.6)Dana Type

(25.6.2)Boracite Group (Trigonal: R3c)

25.6.2.1 Congolite (Fe,Mg,Mn)3B7O13Cl R 3c 3m

25.6.2.2 Trembathite (Mg,Fe)3B7O13Cl R 3c 3m

Strunz Class:

V/L.04-40 V - Nitrates, Carbonates and Borates

V/L - Shelly borates with [BO2]1- to [B6O10]2-

V/L.04 - Boracite - Congolite series

V/L.04-10 Boracite Mg3B7O13Cl P ca2₁ mm2

V/L.04-20 Ericaite (Fe,Mg,Mn)3B7O13Cl P ca2₁ mm2

V/L.04-30 Chambersite Mn3B7O13Cl P ca2₁ mm2

V/L.04-35 Trembathite (Mg,Fe)3B7O13Cl R 3c 3m

V/L.04-40 Congolite (Fe,Mg,Mn)3B7O13Cl R 3c 3m

Other Congolite Information

References:

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

See Also:

Links to other databases for Congolite :
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 -École des Mines de Paris

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

Congolite

(Fe++,Mg,Mn)3B7O13Cl
Dana No: 25.6.2.1 Strunz No: V/L.04-40
Locality:

Notes: