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Bertrandite

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Golconda Mine, Golconda District, Governador Valadares, Doce valley, Minas Gerais, Southeast Region, Brazil
© Rob Lavinsky

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Formula:
Be
 
4
[(OH)
 
2
|Si
 
2
O
 
7
]
System:OrthorhombicColour:Colourless, pale yellow.
Lustre:VitreousHardness:6 - 7
Name:For Emile Bertrand (1844-1909) French mineralogist
This page provides mineralogical data about Bertrandite.

Classification of Bertrandite

IMA status:Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
Strunz 8th edition ID:8/C.07-10
Nickel-Strunz 10th (pending) edition ID:9.BD.05

9 : SILICATES (Germanates)
B : Sorosilicates
D : Si2O7 groups, with additional anions; cations in tetrahedral [4] and greater coordination
Dana 8th edition ID:56.1.1.1

56 : SOROSILICATES Si2O7 Groups, With Additional O, OH, F and H2O
1 : Si2O7 Groups and O, OH, F, and H2O with cations in [4] coordination
Hey's CIM Ref.:14.3.2

14 : Silicates not Containing Aluminum
3 : Silicates of Be
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Type Occurrence of Bertrandite

Co-type Localities:Barbin Quarry, Nantes, Loire-Atlantique, Pays de Loire, France
Petit-Port, Nantes, Loire-Atlantique, Pays de Loire, France
Place of Conservation of Type Material:National School. of Mines, Paris, France
Year of Discovery:1883

Occurrences of Bertrandite

Geological Setting:Granite fissures or miarolitic cavities, pegmatites, greissen. Alteration product of beryl, rarely primary mineral.

Physical Properties of Bertrandite

Lustre:Vitreous
Diaphaneity (Transparency):Transparent
Comment:Pearly on cleavage {001}
Colour:Colourless, pale yellow.
Hardness (Mohs):6 - 7
Cleavage:Perfect
Perfect on {001}
Distinct on {100}{010}{110}
Density (measured):2.59 - 2.6 g/cm3
Density (calculated):2.61 g/cm3

Crystallography of Bertrandite

Crystal System:Orthorhombic
Class (H-M):mm2 - Pyramidal
Space Group:Cmc21
Cell Parameters:a = 8.7135(4) Å, b = 15.268(1) Å, c = 4.5683(3) Å
Ratio:a:b:c = 0.571 : 1 : 0.299
Unit Cell Volume:V 607.76 ų (Calculated from Unit Cell)
Z:4
Morphology:Thin tabular, prismatic to needlelike
Twinning:Common on {011}{021}
Heart or vee shaped.
Crystal Atlas:
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Bertrandite no.19 - Goldschmidt (1913-1926)
Bertrandite no.20 - Goldschmidt (1913-1926)
Bertrandite no.21 - Goldschmidt (1913-1926)

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Optical Data of Bertrandite

Type:Biaxial (-)
RI values: nα = 1.591 nβ = 1.605 nγ = 1.614
2V:Measured: 73° to 81°, Calculated: 76°
Maximum Birefringence:δ = 0.023

Chart shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:Moderate
Dispersion:r < v weak

Chemical Properties of Bertrandite

Formula:
Be
 
4
[(OH)
 
2
|Si
 
2
O
 
7
]
Essential elements:Be, H, O, Si
All elements listed in formula:Be, H, O, Si
Common Impurities:Al,Fe,Ca

Relationship of Bertrandite to other Species

Related Minerals - Nickel-Strunz Grouping):
9.BD.10Hemimorphite
Zn
 
4
[(OH)
 
2
|Si
 
2
O
 
7
] · H
 
2
O
9.BD.15Junitoite
CaZn
 
2
[Si
 
2
O
 
7
] · H
 
2
O
9.BD.20Axinite-(Fe)
Ca
 
2
Fe
2+
 
Al
 
2
[OH|BSi
 
4
O
 
15
]
9.BD.20Axinite-(Mg)
Ca
 
2
MgAl
 
2
[OH|BSi
 
4
O
 
15
]
9.BD.20Axinite-(Mn)
Ca
 
2
Mn
2+
 
Al
 
2
[OH|BSi
 
4
O
 
15
]
9.BD.20Tinzenite
(Ca,Mn
2+
 
,Fe
2+
 
)
 
3
Al
 
2
[OH|BSi
 
4
O
 
15
]
9.BD.25Vistepite
SnMn
 
4
B
 
2
Si
 
4
O
 
16
(OH)
 
2
9.BD.30Boralsilite
Al
 
16
B
 
6
Si
 
2
O
 
27
9.BD.35Werdingite
(Mg,Fe)
 
2
Al
 
14
Si
 
4
B
 
4
O
 
37
Related Minerals - Hey's Index Grouping:
14.3.1Phenakite
Be
 
2
[SiO
 
4
]
14.3.3Beryllite
Be
 
3
[(OH)
 
2
|SiO
 
4
] · H
 
2
O
14.3.4Liberite
Li
 
2
Be[SiO
 
4
]
14.3.5Chkalovite
Na
 
2
BeSi
 
2
O
 
6
14.3.6Eudidymite
NaBeSi
 
3
O
 
7
OH
14.3.7Epididymite
NaBeSi
 
3
O
 
7
OH
14.3.8Gugiaite
Ca
 
2
Be[Si
 
2
O
 
7
]
14.3.9Jeffreyite
(Ca,Na)
 
2
(Be,Al)[Si
 
2
O
 
6
(O,OH)]
14.3.10Semenovite-(Ce)
(Na,Ca)
 
9
Fe
2+
 
(Ce,La)
 
2
[(Si,Be)
 
5
(O,OH,F)
 
12
]
 
4
14.3.11Barylite
BaBe
 
2
[Si
 
2
O
 
7
]
14.3.12Hingganite-(Ce)
Ce
 
2
□Be
 
2
Si
 
2
O
 
8
(OH)
 
2
14.3.13Hingganite-(Yb)
(Yb,Y)Be[OH|SiO
 
4
]
14.3.14Hingganite-(Y)
(Y,Yb,Er)Be[OH|SiO
 
4
]
14.3.15Minasgeraisite-(Y)
Y
 
2
CaBe
 
2
[O|SiO
 
4
]
 
2
14.3.16Sørensenite
Na
 
4
SnBe
 
2
Si
 
6
O
 
16
(OH)
 
4
14.3.17Trimerite
CaMn
2+
2
Be
 
3
[SiO
 
4
]
 
3
14.3.18Chiavennite
CaMnBe
 
2
Si
 
5
O
 
13
(OH)
 
2
·2H
 
2
O
14.3.19Tvedalite
(Ca,Mn)
 
4
Be
 
3
Si
 
6
O
 
17
(OH)
 
4
·3H
 
2
O
14.3.20Harstigite
Ca
 
6
(Mn,Mg)Be
 
4
Si
 
6
(O,OH)
 
24
14.3.21Sverigeite
NaMnMgSnBe
 
2
Si
 
3
O
 
12
(OH)
14.3.22Joesmithite
[(Ca,Pb)][(Ca,Pb)
 
2
][(Mg,Fe
2+
 
)
 
5
][(OH)
 
2
|BeSi
 
7
O
 
22
]
14.3.23Gadolinite-(Y)
Y
 
2
Fe
2+
 
Be
 
2
[O|SiO
 
4
]
 
2
14.3.24Gadolinite-(Ce)
(Ce,La,Nd,Y)
 
2
Fe
2+
 
Be
 
2
[O|SiO
 
4
]
 
2
14.3.25Calciogadolinite
(Y,Ca)
 
2
(Fe,Fe)Be
 
2
Si
 
2
(O,OH)
 
10

Other Names for Bertrandite

Synonyms:
Hessenbergite
German names:
BertranditHessenbergit
Russian names:
Бертрандит
Spanish names:
Bertrandita
Varieties:
Gel-Betrandite

Other Information

Electrical:Pyroelectric
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 Bertrandite

Reference List:Neues Jahrbuch für Mineralogie, Monatshefte (1992): 13-19.

Internet Links for Bertrandite

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  • Raman and XRD data at RRUFF project
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  • Bertrandite details from Handbook of Mineralogy (PDF)
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    Localities for Bertrandite

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