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Bertrandite

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Emile Bertrand
Formula:
Be4Si2O7(OH)2
System:
Orthorhombic
Colour:
Colourless, pale yellow.
Lustre:
Vitreous
Hardness:
6 - 7
Name:
Named in honor of Emile Bertrand (1844 - 16 November 1909), French mineralogist and co-founder of the Société française de Minéralogie.

Classification of Bertrandite

Approved, 'Grandfathered' (first described prior to 1959)
9.BD.05

9 : SILICATES (Germanates)
B : Sorosilicates
D : Si2O7 groups, with additional anions; cations in tetrahedral [4] and greater coordination
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
14.3.2

14 : Silicates not Containing Aluminum
3 : Silicates of Be

Physical Properties of Bertrandite

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} and {110}
Density:
2.59 - 2.6 g/cm3 (Measured)    2.61 g/cm3 (Calculated)

Optical Data of Bertrandite

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

IMA Formula:
Be4Si2O7(OH)2
Elements listed in formula:
Common Impurities:
Al,Fe,Ca

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 needle-like
Twinning:
Common on {011}, {021}; heart- or V-shaped twins.

Crystallographic forms of Bertrandite

Crystal Atlas:
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Bertrandite no.19 - Goldschmidt (1913-1926)
Bertrandite no.20 - Goldschmidt (1913-1926)
Bertrandite no.21 - Goldschmidt (1913-1926)
3d models and HTML5 code kindly provided by www.smorf.nl.

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Occurrences of Bertrandite

Type Occurrence of Bertrandite

Place of Conservation of Type Material:
National School of Mines, Paris, France

Relationship of Bertrandite to other Species

9.BD.10HemimorphiteZn4Si2O7(OH)2 · H2O
9.BD.15JunitoiteCaZn2Si2O7 · H2O
9.BD.20Axinite-(Fe)Ca4Fe22+Al4[B2Si8O30](OH)2
9.BD.20Axinite-(Mg)Ca4Mg2Al4[B2Si8O30](OH)2
9.BD.20Axinite-(Mn)Ca4Mn22+Al4[B2Si8O30](OH)2
9.BD.20TinzeniteCa2Mn42+Al4[B2Si8O30](OH)2
9.BD.25VistepiteMn4SnB2O2(Si2O7)2(OH)2
9.BD.30BoralsiliteAl16B6O30(Si2O7)
9.BD.35WerdingiteMg2Al14Si4B4O37
14.3.1PhenakiteBe2SiO4
14.3.3BerylliteBe3SiO4(OH)2 · H2O
14.3.4LiberiteLi2BeSiO4
14.3.5ChkaloviteNa2BeSi2O6
14.3.6EudidymiteNa2Be2Si6O15 · H2O
14.3.7EpididymiteNa2Be2Si6O15 · H2O
14.3.8GugiaiteCa2BeSi2O7
14.3.9Jeffreyite(Ca,Na)2(Be,Al)Si2(O,OH)7
14.3.10Semenovite-(Ce)(Na,Ca)9Fe2+Ce2(Si,Be)20(O,OH,F)48
14.3.11BaryliteBaBe2Si2O7
14.3.12Hingganite-(Ce)BeCe(SiO4)(OH)
14.3.13Hingganite-(Yb)BeYb(SiO4)(OH)
14.3.14Hingganite-(Y)(Y,REE,Ca)2(□,Fe2+)Be2[SiO4]2(OH)2
14.3.15Minasgeraisite-(Y)CaBe2Y2(SiO4)2O2
14.3.16SørenseniteNa4Be2Sn(Si3O9)2 · 2H2O
14.3.17TrimeriteCaBe3Mn22+(SiO4)3
14.3.18ChiavenniteCaMn2+(BeOH)2Si5O13 · 2H2O
14.3.19TvedaliteCa4Be3Si6O17(OH)4 · 3H2O
14.3.20HarstigiteCa6Be4Mn2+(SiO4)2(Si2O7)2(OH)2
14.3.21SverigeiteNaBe2Mn22+SnSi3O12(OH)
14.3.22JoesmithitePbCa2Mg3Fe23+(Si6Be2)O22(OH)2
14.3.23Gadolinite-(Y)Fe2+Be2Y2(SiO4)2O2
14.3.24Gadolinite-(Ce)Fe2+Be2Ce2(SiO4)2O2
14.3.25Calciogadolinite-(Y)(YCa)2Fe3+Be2[SiO4]2O2

Other Names for Bertrandite

Name in Other Languages:
Simplified Chinese:羟硅铍石
Spanish:Bertrandita
Traditional Chinese:羥矽鈹石

Other Information

Electrical:
Pyroelectric
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 Bertrandite

Reference List:
Damour, A.A. (1883) Note et analyse sur le nouveau miné des environs de Nantes. Bulletin de la Société Minéralogique de France: 6: 252-254.

Solov'eva, L.P., Belov, N.V. (1965) Precise determination of the crystal structure of bertrandite Be4[Si2O7](OH)2. Soviet Physics - Crystallography: 9: 458-460.

Henderson, W.A., Jr. (1975) The Bertrandites of Connecticut. The Mineralogical Record: 6(3): 114-123.

Hazen, R.M., Au, A.Y. (1986) High-pressure crystal chemistry of phenakite (Be2SiO4) and bertrandite (Be4Si2O7(OH)2). Physics and Chemistry of Minerals: 13: 69-78.

Hofmeister, A.M., Hoering, T.C., Virgo, D. (1987) Vibrational spectroscopy of beryllium aluminosilicates: heat capacity calculations from band assignments. Physics and Chemistry of Minerals: 14: 205-224.

Giuseppetti, G., Tadini, C., Mattioli, V. (1992) Bertrandite: Be4Si2O7(OH)2, from Val Vigezzo (NO) Italy: the X-ray structural refinement. Neues Jahrbuch für Mineralogie, Monatshefte: 1992: 13-19.

Internet Links for Bertrandite

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Specimens:
The following Bertrandite specimens are currently listed for sale on minfind.com.

Localities for Bertrandite

Mineral and/or Locality  
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