Bertrandite Mineral Data

Bertrandite Mineral Data +

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General Bertrandite Information

Chemical Formula:

Be4Si2O7(OH)2

Composition:

Molecular Weight = 238.23 gm

Beryllium 15.13 % Be 42.00 % BeO

Silicon 23.58 % Si 50.44 % SiO₂

Hydrogen 0.85 % H 7.56 % H₂O

Oxygen 60.44 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

Be₄(Si₂O₇)(OH)₂

Environment:

Commonly found in Be-bearing pegmatites and may be derived from the alteration of beryl.

IMA Status:

Valid Species (Pre-IMA) 1883

Locality:

Discovered at near Nantes, Loire-Inferieure, France. Also found at Irkutka and Altai Mountains, Siberia, Russia. Link to MinDat.org Location Data.

Name Origin:

Named after the French mineralogist, E. Bertrand.

Synonym:

ICSD 202360

PDF 24-509

Bertrandite Image

Images:

Bertrandite

Comments: Colorless prismatic crystals of bertrandite on matrix with pale pink rhombohedral crystals of rhodochrosite.
Location: Yiaoguanshen mine, Hunan Province, China. Scale: 3.5 x 4 cm.
© Dan Weinrich

Images:

Bertrandite

Comments: Fan-like clusters of bertrandite crystals with brown rhodochrosite and quartz.
Location: Kara Oba, Kazakhstan. Scale: Crystal size 1.1 cm.
© John Veevaert

Bertrandite Crystallography

Axial Ratios:

a:b:c =1.7514:1:0.5224

Cell Dimensions:

a = 15.22, b = 8.69, c = 4.54, Z = 4; V = 600.47 Den(Calc)= 2.64

Crystal System:

Orthorhombic - PyramidalH-M Symbol (mm2) Space Group: Ccm21

$Help on X Ray Diffraction:$ X Ray Diffraction:

By Intensity(I/I_o): 4.38(1), 3.19(0.9), 2.54(0.8),

Crystal Structure:

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Downs J W , Ross F K , American Mineralogist , 72 (1987) p.979-983, Neutron-diffraction study of bertrandite, Note: O2y has been corrected

View Additional jPOWD Structure files for Bertrandite
[1] [2] [3]

Physical Properties of Bertrandite

Cleavage:

[001] Perfect, [110] Distinct, [101] Distinct

Color:

Colorless, Pale yellow.

Density:

2.59 - 2.6, Average = 2.59

Diaphaniety:

Translucent to transparent

Fracture:

Brittle - Generally displayed by glasses and most non-metallic minerals.

Habit:

Crystalline - Fine - Occurs as well-formed fine sized crystals.

Habit:

Prismatic - Crystals Shaped like Slender Prisms (e.g. tourmaline).

Habit:

Tabular - Form dimensions are thin in one direction.

Hardness:

6-7 - Orthoclase-Quartz

Luminescence:

None.

Luster:

Vitreous (Glassy)

Magnetism:

Nonmagnetic

Streak:

white

Optical Properties of Bertrandite

Gladstone-Dale:

CI meas= -0.005 (Superior) - where the CI = (1-KPDmeas/KC)
CI calc= 0.012 (Superior) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2285,KPDmeas= 0.2325,KC= 0.2314

Optical Data:

Biaxial (-), a=1.591, b=1.605, g=1.614, bire=0.0230, 2V(Calc)=76, 2V(Meas)=73-81. Dispersion none.

Pleochroism (x):

none.

Pleochroism (y):

none.

Pleochroism (z):

none.

Calculated Properties of Bertrandite

Electron Density:

r_electron=2.57 gm/cc
note: r_Bertrandite=2.60 gm/cc.

Fermion Index

Fermion Index = 0.16262
Boson Index = 0.83738

Photoelectric:

PE_Bertrandite= 1.07 barns/electron
U=PE_Bertrandite x r_electron= 2.75 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Bertrandite is Not Radioactive

Bertrandite Classification

Dana Class:

56.1.1.1 (56)Sorosilicate Si2O7 Groups and O, OH, F. and H2O

(56.1)with cations in [4] coordination

(56.1.1)Dana Group

56.1.1.1 Bertrandite Be4Si2O7(OH)2 Ccm21 mm2

Strunz Class:

VIII/C.07-10 VIII - Silicates

VIII/C - Sorosilicates with [Si2O7]6-, with anions unfamiliar to tetraheders [O,OH,F]

VIII/C.07 - Bertrandite - Strontiochevkinite series

VIII/C.07-10 Bertrandite Be4Si2O7(OH)2 Ccm21 mm2

VIII/C.07-210 Chevkinite-(Ce) (Ce,La,Ca,Th)4(Fe,Mg)2(Ti,Fe)3Si4O22 C 2/m 2/m

Other Bertrandite Information

References:

NAME( Ford32) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Ford32)

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Print or Cut-and-Paste your Bertrandite Specimen Label here :

Bertrandite

Be4Si2O7(OH)2
Dana No: 56.1.1.1 Strunz No: VIII/C.07-10
Locality:

Notes: