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Congolite

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Brazzaville (Renéville; Djoué), Brazzaville Region (Renéville Region), Republic of Congo (Brazzaville)
© 2007, JGW

Formula:
(Fe
2+
 
,Mg)
 
3
B
 
7
O
 
13
Cl
System:TrigonalHardness:6½ - 7½
Dimorph of:Ericaite


Boracite Group. The Fe2+ analogue of Trembathite. The trigonal dimorph of Ericaite.

Classification of Congolite

IMA status:Approved
Strunz 8th edition ID:5/L.04-40
Nickel-Strunz 10th (pending) edition ID:6.GA.10

6 : BORATES
G : Heptaborates and other megaborates
A : Tekto-heptaborates
Dana 8th edition ID:25.6.2.1

25 : ANHYDROUS BORATES CONTAINING HYDROXYL OR HALOGEN
6 : Hexaborates
Hey's CIM Ref.:10.1.19

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

Type Locality:Brazzaville (Renéville; Djoué), Brazzaville Region (Renéville Region), Republic of Congo (Brazzaville)
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
Maximum Birefringence:δ = 0.024

Chart shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:High

Chemical Properties of Congolite

Formula:
(Fe
2+
 
,Mg)
 
3
B
 
7
O
 
13
Cl
Essential elements:B, Cl, Fe, O
All elements listed in formula:B, Cl, Fe, Mg, O

Relationship of Congolite to other Species

Related Minerals - Nickel-Strunz Grouping):

- +
6.GA.05Boracite
Mg
 
3
[Cl|B
 
7
O
 
13
]
6.GA.05Chambersite
Mn
2+
3
[Cl|B
 
7
O
 
13
]
6.GA.05Ericaite
Fe
2+
3
[Cl|B
 
7
O
 
13
]
6.GA.10Trembathite
(Mg,Fe)
 
3
B
 
7
O
 
13
Cl
6.GA.30Korzhinskite
CaB
 
2
O
 
4
·H
 
2
O
Related Minerals - Hey's Index Grouping:

- +
10.1.1Teepleite
Na
 
2
[Cl|B(OH)
 
4
]
10.1.2Bandylite
Cu[Cl|B(OH)
 
4
]
10.1.3Berborite
Be
 
2
[(OH,F)|BO
 
3
] · H
 
2
O
10.1.4Fluoborite
Mg
 
3
[(F,OH)
 
3
|BO
 
3
]
10.1.5Boracite
Mg
 
3
[Cl|B
 
7
O
 
13
]
10.1.6Karlite
Mg
 
7
[(OH,Cl)
 
5
|(BO
 
3
)
 
3
]
10.1.7Shabynite
Mg
 
5
[(Cl,OH)
 
2
|(OH)
 
5
|BO
 
3
] · 4H
 
2
O
10.1.8/9/10Hilgardite
Ca
 
2
B
 
5
O
 
9
Cl·H
 
2
O
10.1.11Solongoite
Ca
 
2
(H
 
3
B
 
3
O
 
7
)(OH)Cl
10.1.12Hydrochlorborite
Ca
 
4
B
 
8
O
 
15
Cl
 
2
·21H
 
2
O
10.1.13Ekaterinite
Ca
 
2
[(Cl,OH)
 
2
|B
 
4
O
 
7
] · 2H
 
2
O
10.1.14Volkovskite
KCa
 
4
[B
 
5
O
 
8
OH]
 
4
[B(OH)
 
3
]
 
2
Cl·4H
 
2
O
10.1.15Chelkarite
CaMgB
 
2
O
 
4
(Cl,OH)
 
2
·5H
 
2
O Or near, with Cl:OH = 3:1
10.1.16Johachidolite
CaAlB
 
3
O
 
7
10.1.17Satimolite
KNa
 
2
Al
 
4
[Cl|B
 
2
O
 
5
]
 
3
 · 13H
 
2
O
10.1.18Chambersite
Mn
2+
3
[Cl|B
 
7
O
 
13
]
10.1.20Ericaite
Fe
2+
3
[Cl|B
 
7
O
 
13
]

Other Names for Congolite

Synonyms:
IMA1971-030
Other Languages:
German:Congolit
Russian:Конголит
Spanish:Congolita

Other Information

Health Warning: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

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  • Raman and XRD data at RRUFF project
  • American Mineralogist Crystal Structure Database
  • Search for Congolite in the Natural History Museum (London) online catalogue
  • Congolite details from Handbook of Mineralogy (PDF)
    • Mineral Dealers:
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    Localities for Congolite

    Hide Locality List
    The 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. ? 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.
    		Canadian Mineralogist: 43: 1469-1487.
        • Sussex
          • 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
    Republic of Congo (Brazzaville)
     
    • Brazzaville Region (Renéville Region)
    		American Mineralogist (1972): 57: 1315.
    Mineral and/or Locality
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