Varennesite Mineral Data

Varennesite Mineral Data +

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General Varennesite Information

Chemical Formula:

Na8Mn++2Si10O25(OH,Cl)2·12(H2O)

Composition:

Molecular Weight = 1,234.05 gm

Sodium 14.90 % Na 20.09 % Na₂O

Manganese 8.90 % Mn 11.50 % MnO

Silicon 22.76 % Si 48.69 % SiO₂

Hydrogen 2.08 % H 18.61 % H₂O

Chlorine 1.44 % Cl 1.44 % Cl

- % Cl -0.32 % -O=Cl₂

Oxygen 49.91 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

Na₈Mn²⁺₂Si₁₀O₂₅(OH)_1.5Cl_0.5·12(H₂O)

Environment:

As a primary, late-stage mineral in a sill.

IMA Status:

Approved IMA 1995

Locality:

Demix-Varennes quarry, which lies between the villages of Varennes and Saint-Amable, in Vercheres County, Quebec Link to MinDat.org Location Data.

Name Origin:

For the locality.

Synonym:

ICSD 81583

IMA1994-017

PDF 49-1860

Varennesite Image

Images:

Varennesite

Comments: Brown to tan varennesite crystal embedded in nepheline-syenite rock.
Location: DeMix Quarry, Varennes, Quebec, Canada. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Varennesite Crystallography

Axial Ratios:

a:b:c =0.8951:1:1.1716

Cell Dimensions:

a = 13.447, b = 15.022, c = 17.601, Z = 4; V = 3,555.42 Den(Calc)= 2.31

Crystal System:

Orthorhombic - DipyramidalH-M Symbol (2/m 2/m 2/m) Space Group: C mcm

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

By Intensity(I/I_o): 10.049(1), 2.718(0.5), 8.823(0.5),

Forms:

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Crystal Structure:

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Grice J D , Gault R A , The Canadian Mineralogist , 33 (1995) p.1073-1081, Varennesite, a new species of hydrated Na-Mn silicate with a unique, monophyllosilicate structure

Physical Properties of Varennesite

Cleavage:

[010] Good

Color:

Pale brownish yellow, Orange.

Density:

2.31

Diaphaniety:

Translucent to transparent

Fracture:

Brittle - Conchoidal - Very brittle fracture producing small, conchoidal fragments.

Habit:

Euhedral Crystals - Occurs as well-formed crystals showing good external form.

Habit:

Tabular - Form dimensions are thin in one direction.

Hardness:

4 - Fluorite

Luminescence:

Non-fluorescent.

Luster:

Vitreous (Glassy)

Streak:

white

Optical Properties of Varennesite

Gladstone-Dale:

CI meas= -0.018 (Superior) - where the CI = (1-KPDmeas/KC)
CI calc= -0.018 (Superior) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2341,KPDmeas= 0.2341,KC= 0.2299

Optical Data:

Biaxial (+), a=1.532, b=1.54, g=1.55, bire=0.0180, 2V(Calc)=86, 2V(Meas)=89. Dispersion weak, r < v.

Pleochroism (x):

pale yellow.

Pleochroism (y):

pale yellow.

Pleochroism (z):

yellowish green.

Calculated Properties of Varennesite

Electron Density:

r_electron=2.32 gm/cc
note: r_Varennesite=2.31 gm/cc.

Fermion Index

Fermion Index = 0.01087
Boson Index = 0.98913

Photoelectric:

PE_Varennesite= 3.44 barns/electron
U=PE_Varennesite x r_electron= 7.99 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Varennesite is Not Radioactive

Varennesite Classification

Dana Class:

72.5.5.1 (72)Phyllosilicate Two-Dimensional Infinite Sheets with Other Than Six-Membered Rings

(72.5)with corrugated and complex layers

(72.5.5)Dana Group

72.5.5.1 Varennesite Na8Mn2Si10O25(OH,Cl)2·12(H2O) C mcm 2/m 2/m 2/m

Strunz Class:

VIII/H.28-100 VIII - Silicates

VIII/H - Phyllosilicates (layered) Mica minerals with other simple layers, [Si6O15]6- and others

VIII/H.28 - Pyrosmalite series

VIII/H.28-10 Ferropyrosmalite (Fe,Mn)8Si6O15(OH,Cl)10 P 3m1 3 2/m

VIII/H.28-20 Manganpyrosmalite (Mn,Fe)8Si6O15(OH,Cl)10 P 3m1 3 2/m

VIII/H.28-30 Brokenhillite* (Mn,Fe)32[Si24O60]OH29Cl11 P 6₃mc 6mm

VIII/H.28-40 Nelenite (Mn,Fe)16Si12As3O36(OH)17 R 3m 3 2/m

VIII/H.28-50 Schallerite Mn16[AsO2OH][Si12O30](OH)14 P 3m1 ? 3m

VIII/H.28-70 Friedelite Mn8Si6O15(OH,Cl)10 C 2/m 2/m

VIII/H.28-80 Mcgillite (Mn,Fe)8Si6O15(OH)8Cl2 C 2/m 2/m

VIII/H.28-90 Bementite Mn8Si6O15(OH)10 P 2₁/c 2/m

VIII/H.28-100 Varennesite Na8Mn2Si10O25(OH,Cl)2·12(H2O) C mcm 2/m 2/m 2/m

Other Varennesite Information

References:

NAME( MinRec) PHYS. PROP.(Am.Min.,Vol.81,p767,1996) OPTIC PROP.(MinRec)

See Also:

Links to other databases for Varennesite :
1 -Am. Min. Crystal Structure Database 2 -Athena 3 -Google Images 4 -Google Scholar 5 -MinDAT 6 -MinMax(Deutsch) 7 -MinMax(English) 8 -Mineralienatlas (Deutsch) 9 -QUT Mineral Atlas 10 - WWW-MINCRYST

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Varennesite

Na8Mn++2Si10O25(OH,Cl)2·12(H2O)
Dana No: 72.5.5.1 Strunz No: VIII/H.28-100
Locality:

Notes: