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About CongoliteHide

Flag of the Republic of the Congo
Pale red, pink
6½ - 7½
Crystal System:
Member of:
Named by E. Wendling, R.V. Hodenberg, and R. Kühn in 1972 after the country where the mineral was first discovered, the Republic of Congo (Brazzaville).
Dimorph of:
Boracite Group. The Fe2+ analogue of Trembathite. The trigonal dimorph of Ericaite.

Classification of CongoliteHide

First Published:

G : Heptaborates and other megaborates
A : Tekto-heptaborates

6 : Hexaborates

10 : Borates with other anions
1 : Borates with halide

Physical Properties of CongoliteHide

Pale red, pink
6½ - 7½ on Mohs scale

Optical Data of CongoliteHide

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:

Chemical Properties of CongoliteHide

IMA Formula:

Crystallography of CongoliteHide

Crystal System:
Class (H-M):
3m - Ditrigonal Pyramidal
Space Group:
Cell Parameters:
a = 8.62 Å, c = 21.05 Å
a:c = 1 : 2.442
Unit Cell V:
1,354.56 ų (Calculated from Unit Cell)

Type Occurrence of CongoliteHide

General Appearance of Type Material:
grains from drill core

Synonyms of CongoliteHide

Other Language Names for CongoliteHide


Relationship of Congolite to other SpeciesHide

Member of:
Other Members of this group:
BoraciteMg3(B7O13)ClOrth. mm2 : Pca21
ChambersiteMn2+3(B7O13)ClOrth. mm2 : Pca21

Common AssociatesHide

Associated Minerals Based on Photo Data:
Sylvite2 photos of Congolite associated with Sylvite on mindat.org.

Related Minerals - Nickel-Strunz GroupingHide

6.GA.05BoraciteMg3(B7O13)ClOrth. mm2 : Pca21
6.GA.05ChambersiteMn2+3(B7O13)ClOrth. mm2 : Pca21
6.GA.30KorzhinskiteCa(B2O4) · H2O

Related Minerals - Dana Grouping (8th Ed.)Hide,Fe)3(B7O13)ClTrig.

Related Minerals - Hey's Chemical Index of Minerals GroupingHide

10.1.1TeepleiteNa2[B(OH)4]ClTet. 4/mmm (4/m 2/m 2/m) : P4/nmm
10.1.2BandyliteCu[B(OH)4]ClTet. 4/mmm (4/m 2/m 2/m) : P4/nmm
10.1.3BerboriteBe2(BO3)(OH,F) · H2OTrig.
10.1.5BoraciteMg3(B7O13)ClOrth. mm2 : Pca21
10.1.7ShabyniteMg5(BO3)(OH)5(Cl,OH)2 · 4H2OMon.
10.1.8/9/10HilgarditeCa2B5O9Cl · H2OTric. 1 : P1
10.1.12HydrochlorboriteCa4B8O15Cl2 · 21H2OMon.
10.1.13EkateriniteCa2(B4O7)(Cl,OH)2 · 2H2OHex.
10.1.14VolkovskiteKCa4[B5O8OH]4[B(OH)3]2Cl · 4H2OTric. 1 : P1
10.1.15ChelkariteCaMgB2O4(Cl,OH)2 · 5H2O Or near, with Cl:OH = 3:1Orth.
10.1.16JohachidoliteCaAlB3O7Orth. mmm (2/m 2/m 2/m) : Cmma
10.1.17SatimoliteKNa2(Al5Mg2)[B12O18(OH)12](OH)6Cl4·4H2OTrig. 3m (3 2/m) : R3m
10.1.18ChambersiteMn2+3(B7O13)ClOrth. mm2 : Pca21

Other InformationHide

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 CongoliteHide

Reference List:
Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Wendling, E., Hodenberg, R.V., Kühn, R. (1972) Congolit, der trigonale eisenboracit. Kali und Steinsalz: 6: 1-3.
Fleischer, M. (1972) New mineral names. American Mineralogist: 57: 1311-1317.
Dowty, E., Clark, J.R. (1973) Crystal-structure refinements for orthorhombic boracite, Mg3B7O13Cl, and a trigonal, iron-rich analogue. Zeitschrift für Kristallographie: 138: 64-99.
Nelmes, R.J. (1974) Structural studies of boracites. A review of the properties of boracites. Journal of Physics C: Solid State Physics: 7: 3841-3855.
Mendoza-Alvarez, M.E., Yvon, K., Depmeier, W., Schmid, H. (1985) Structure refinement of trigonal iron-chlorine boracite. Acta Crystallographica: C41: 1551-1552.
Burns, P.C. (1995) X-ray powder diffraction data for the identification of boracite-group minerals. Powder Diffraction: 10: 250-260.
Burns, P.C., Carpenter, M.A. (1996) Phase transitions in the series boracite-trembathite-congolite: phase relations. Canadian Mineralogist: 34: 881-892.
Grew, E.S., Anovitz, L.M. (1996) BORON: Mineralogy, Petrology and Geochemistry, second edition, as revised (2002).
Burns, P.C., Carpenter, M.A. (1997) Phase transitions in the series boracite – trembathite – congolite: an infrared spectroscopic study. The Canadian Mineralogist: 35: 189-202.
Grice, J.D., Gault, R.A., Van Velthuizen, J. (2005) Borate minerals of the Penobsquis and Millstream deposits, southern New Brunswick, Canada. The Canadian Mineralogist: 43: 1469-1487.
Wachowiak, J., Pieczka, A., (2012) Congolite and trembathite from the Kłodawa Salt Mine, Central Poland: records of the thermal history of the parental salt dome. The Canadian Mineralogist: 50: 1387-1399.

Internet Links for CongoliteHide

Localities for CongoliteHide

This 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.

Locality ListHide

- This locality has map coordinates listed. - This locality has estimated coordinates. ⓘ - Click for further information on this occurrence. ? - Indicates mineral may be doubtful at this locality. - Good crystals or important locality for species. - World class for species or very significant. (TL) - Type Locality for a valid mineral species. (FRL) - First Recorded Locality for everything else (eg varieties). Struck out - Mineral was erroneously reported from this locality. Faded * - Never found at this locality but inferred to have existed at some point in the past (eg from pseudomorphs.)

All localities listed without proper references should be considered as questionable.
  • 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
Grice, J.D., Gault, R.A., Van Velthuizen, J. (2005) Borate minerals of the Penobsquis and Millstream deposits, southern New Brunswick, Canada. The Canadian Mineralogist: 43: 1469-1487.
  • Thuringia
    • Bleicherode
Fleischer M (1972) New mineral names. American Mineralogist 57, 1311-1317
  • Greater Poland
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]; Wachowiak, J., Pieczka, A. (2016): Motukoreaite from the Kłodawa Salt Dome, Central Poland. Mineralogical Magazine, 80, 277-289
Republic of Congo (Brazzaville)
  • Brazzaville Department
American Mineralogist (1972): 57: 1315.
American Mineralogist (1972): 57: 1315.
  • England
    • North Yorkshire
      • Redcar and Cleveland
        • Loftus
Bart Cannon analyses
Mineral and/or Locality  
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