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Congolite

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Formula:
(Fe2+,Mg)3(B7O13)Cl
System:
Trigonal
Hardness:
6½ - 7½
Member of:
Dimorph of:
Boracite Group. The Fe2+ analogue of Trembathite. The trigonal dimorph of Ericaite.

Classification of Congolite

Approved
6.GA.10

6 : BORATES
G : Heptaborates and other megaborates
A : Tekto-heptaborates
25.6.2.1

25 : ANHYDROUS BORATES CONTAINING HYDROXYL OR HALOGEN
6 : Hexaborates
10.1.19

10 : Borates with other anions
1 : Borates with halide
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Type Occurrence of Congolite

Year of Discovery:
1972

Physical Properties of Congolite

Hardness (Mohs):
6½ - 7½

Crystallography of Congolite

Crystal System:
Trigonal
Cell Parameters:
a = 8.62Å, c = 21.05Å
Ratio:
a:c = 1 : 2.442
Unit Cell Volume:
V 1,354.56 ų (Calculated from Unit Cell)

Optical Data of Congolite

Type:
Uniaxial (-)
RI values:
nω = 1.755 nε = 1.731
Max Birefringence:
δ = 0.024
Image shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:
High

Chemical Properties of Congolite

Formula:
(Fe2+,Mg)3(B7O13)Cl
Essential elements:
All elements listed in formula:

Relationship of Congolite to other Species

Member of:
Other Members of Group:
BoraciteMg3(B7O13)Cl
ChambersiteMn32+(B7O13)Cl
EricaiteFe32+(B7O13)Cl
Trembathite(Mg,Fe)3(B7O13)Cl
6.GA.05BoraciteMg3(B7O13)Cl
6.GA.05ChambersiteMn32+(B7O13)Cl
6.GA.05EricaiteFe32+(B7O13)Cl
6.GA.10Trembathite(Mg,Fe)3(B7O13)Cl
6.GA.30KorzhinskiteCa(B2O4) · H2O
10.1.1TeepleiteNa2[B(OH)4]Cl
10.1.2BandyliteCu[B(OH)4]Cl
10.1.3BerboriteBe2(BO3)(OH,F) · H2O
10.1.4FluoboriteMg3(BO3)(F,OH)3
10.1.5BoraciteMg3(B7O13)Cl
10.1.6KarliteMg7(BO3)3(OH,Cl)5
10.1.7ShabyniteMg5(BO3)(OH)5(Cl,OH)2 · 4H2O
10.1.8/9/10HilgarditeCa2B5O9Cl · H2O
10.1.11SolongoiteCa2(H3B3O7)(OH)Cl
10.1.12HydrochlorboriteCa4B8O15Cl2 · 21H2O
10.1.13EkateriniteCa2(B4O7)(Cl,OH)2 · 2H2O
10.1.14VolkovskiteKCa4[B5O8OH]4[B(OH)3]2Cl · 4H2O
10.1.15ChelkariteCaMgB2O4(Cl,OH)2 · 5H2O Or near, with Cl:OH = 3:1
10.1.16JohachidoliteCaAlB3O7
10.1.17SatimoliteKNa2Al4[Cl|B2O5]3 · 13H2O
10.1.18ChambersiteMn32+(B7O13)Cl
10.1.20EricaiteFe32+(B7O13)Cl

Other Names for Congolite

Name in Other Languages:
German:Congolit
Spanish:Congolita

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 Congolite

Reference List:
American Mineralogist (1972): 57: 1315.

Zeitschrift für Kristallographie: 138: 64-99.

Burns, P.C. and Carpenter, M.A. (1996) Phase transitions in the series boracite-trembathite-congolite: phase relations. Canadian Mineralogist: 34: 881-892.

Grew, E.S., and Anovitz, L.M. (1996) BORON: Mineralogy, Petrology and Geochemistry, second edition, as revised (2002).

Internet Links for Congolite

Localities for Congolite

map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
(TL) indicates type locality for a valid mineral species. (FRL) indicates first recorded locality for everything else. ? indicates mineral may be doubtful at this locality. All other localities listed without reference should be considered as uncertain and unproven until references can be found.
Canada
 
  • New Brunswick
    • Kings Co.
      • Cardwell Parish
CM 43, 1469-1487
Grice, J. L. (2002): Borate Minerals from the Penobsquis and Millstream Deposits of Southern New Brunswick, Canada. Bergverksmuseets Skrift 20, 27-33
      • Studholm Parish
Canadian Mineralogist: 43: 1469-1487.
Poland
 
  • Wielkopolskie
PIECZKA, A. & WACHOWIAK, J. (2012) CONGOLITE FROM THE KŁODAWA SALT MINE (CENTRAL POLAND) AND ITS IMPORTANCE AT EVALUATION OF METAMORPHIC CONDITIONS IN THE SALT DOME. Acta Mineralogica-Petrographica, Abstract Series, Szeged, Vol. 7, 2012 , 107. [http://www.mineral.hermuz.hu/acta_07/pdf/107-Pieczka.pdf]
Republic of Congo (Brazzaville)
 
  • Brazzaville Department
American Mineralogist (1972): 57: 1315.
American Mineralogist (1972): 57: 1315.
UK
 
  • England
    • North Yorkshire
      • Loftus
Bart Cannon analyses
Mineral and/or Locality  
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