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General Tephroite Information

Help on Chemical  Formula: Chemical Formula: Mn2SiO4
Help on Composition: Composition: Molecular Weight = 201.96 gm
   Manganese  54.41 %  Mn   70.25 % MnO
   Silicon    13.91 %  Si   29.75 % SiO2
   Oxygen     31.69 %  O
             ______        ______ 
             100.00 %      100.00 % = TOTAL OXIDE
Help on Empirical Formula: Empirical Formula: Mn2+2(SiO4)
Help on Environment: Environment: Contact metamorphism of manganese bearing rocks.
Help on IMA Status: IMA Status: Valid Species (Pre-IMA) 1823
Help on Locality: Locality: Franklin and Sparta, New Jersey, USA. Link to MinDat.org Location Data.
Help on Name Origin: Name Origin: From the Greek tephros - "ash gray" for its color.
Help on Synonym: Synonym: ICSD 100433
  PDF 35-748
 

Tephroite Image

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Tephroite

Comments: Sharp crystals of tephroite to 1.2 cm across.
Location: N'Chwaning Mine, Kalahari Manganese Field, Northern Cape Province, South Africa. Scale: Picture size 5 cm.
© John Veevaert

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Tephroite   Ericssonite   Orthoericssonite

Comments: Dark brown ericssonite, intergrown with orthoericssonite, with pink rhodonite, light brown diopside (var. schefferite) and gray tephroite.
Location: Langban, Varmland, Sweden. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

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Tephroite   Johnbaumite

Comments: Violet crystalline massive johnbaumite with brown tephroite.
Location: Jacobsberg, Varmland, Sweden. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Tephroite Crystallography

Help on Axial Ratios: Axial Ratios: a:b:c =0.4666:1:0.5862
Help on Cell Dimensions: Cell Dimensions: a = 4.76, b = 10.2, c = 5.98, Z = 4; V = 290.34 Den(Calc)= 4.62
Help on Crystal System: Crystal System: Orthorhombic - DipyramidalH-M Symbol (2/m 2/m 2/m) Space Group: P nma
Help on X Ray Diffraction: X Ray Diffraction: By Intensity(I/Io): 2.56(1), 2.86(0.85), 3.61(0.85),
Click Here for Large Tephroite Structure Window Crystal Structure:

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Francis C A , Ribbe P H , American Mineralogist , 65 (1980) p.1263-1269, The forsterite-tephroite series: I. Crystal structure refinements, Te 91, olivine

 

Physical Properties of Tephroite

Help on Cleavage: Cleavage: [010] Indistinct
Help on Color: Color: Gray, Olive green, Bluish green, Red, Reddish brown.
Help on Density: Density: 4.11 - 4.39, Average = 4.25
Help on Diaphaniety: Diaphaniety: Transparent to translucent
Help on Fracture: Fracture: Brittle - Conchoidal - Very brittle fracture producing small, conchoidal fragments.
Help on Habit: Habit: Granular - Generally occurs as anhedral to subhedral crystals in matrix.
Help on Habit: Habit: Massive - Granular - Common texture observed in granite and other igneous rock.
Help on Habit: Habit: Prismatic - Crystals Shaped like Slender Prisms (e.g. tourmaline).
Help on Hardness: Hardness: 6.5 - Pyrite
Help on Luminescence: Luminescence: None.
Help on Luster: Luster: Vitreous - Greasy
Help on Magnetism: Magnetism: Nonmagnetic
Help on Streak: Streak: gray
 

Optical Properties of Tephroite

Help on Gladstone-Dale: Gladstone-Dale: CI meas= 0.054 (Good) - where the CI = (1-KPDmeas/KC)
CI calc= 0.13 (Poor) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.1743,KPDmeas= 0.1895,KC= 0.2003
Help on Optical Data: Optical Data: Biaxial (+), a=1.759, b=1.797, g=1.86, bire=0.1010, 2V(Calc)=78, 2V(Meas)=60-70. Dispersion none.
Help on Pleochroism (x): Pleochroism (x): pale amber.
Help on Pleochroism (y): Pleochroism (y): orange yellow.
Help on Pleochroism (z): Pleochroism (z): pale amber.
 

Calculated Properties of Tephroite

Help on Electron Density: Electron Density:

relectron=4.04 gm/cc
note: rTephroite =4.25 gm/cc.

Help on Fermion Index Fermion Index Fermion Index = 0.00664
Boson Index = 0.99336
Help on Photoelectric: Photoelectric:

PETephroite = 14.67 barns/electron
U=PETephroite x relectron= 59.28 barns/cc.

Help on Radioactivity: Radioactivity: GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Tephroite is Not Radioactive

 

Tephroite Classification

Help on  Dana Class: Dana Class: 51.3.1.4 (51)Nesosilicate Insular SiO4 Groups Only
  (51.3)with all cations in octahedral [6] coordination
  (51.3.1)Olivine group
 
51.3.1.0 Olivine* (Mg,Fe)2SiO4 Pbnm 2/m 2/m 2/m
 
51.3.1.1 Fayalite Fe2SiO4 Pbnm 2/m 2/m 2/m
 
51.3.1.2 Forsterite Mg2SiO4 Pbnm 2/m 2/m 2/m
 
51.3.1.3 Liebenbergite (Ni,Mg)2SiO4 Pbnm 2/m 2/m 2/m
 
51.3.1.4 Tephroite Mn2SiO4 P nma 2/m 2/m 2/m
 
51.3.1.5 Laihunite FeFe2(SiO4)2 P 21/b 2/m
Help on  Strunz Class: Strunz Class: VIII/A.04-30 VIII - Silicates
  VIII/A - Nesosilicates with [SiO4]4-groups, cations of octahedral orientation [6]
  VIII/A.04 - Olivine group
 
VIII/A.04-10 Forsterite Mg2SiO4 Pbnm 2/m 2/m 2/m
 
VIII/A.04-20 Fayalite Fe2SiO4 Pbnm 2/m 2/m 2/m
 
VIII/A.04-30 Tephroite Mn2SiO4 P nma 2/m 2/m 2/m
 
VIII/A.04-40 Liebenbergite (Ni,Mg)2SiO4 Pbnm 2/m 2/m 2/m
 
VIII/A.04-50 Laihunite FeFe2(SiO4)2 P 21/b 2/m
 

Other Tephroite Information

Help on References: References: NAME( Duda&Rejl90) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Mason68)
Help on See Also: See Also: Links to other databases for Tephroite :
1 -Am. Min. Crystal Structure Database 2 - Amethyst Galleries' Mineral Gallery 3 -Athena 4 - CalTech Mineral Spectroscopy 5 - Crocoite.com Mineral Locations 6 - EUROmin Project 7 - Franklin Minerals(Dunn) 8 - Franklin Minerals(Palache) 9 -Google Images 10 -Google Scholar 11 -Handbook of Mineralogy (MinSocAm) 12 -Handbook of Mineralogy (UofA) 13 -MinDAT 14 -MinMax(Deutsch) 15 -MinMax(English) 16 - Mineral and Gemstone Kingdom 17 -Mineralienatlas (Deutsch) 18 -QUT Mineral Atlas 19 - Scandinavian mineral gallery 20 -University of Colorado - Mineral Structure Data 21 - WWW-MINCRYST 22 -École des Mines de Paris

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Tephroite

Mn2SiO4
Dana No: 51.3.1.4 Strunz No: VIII/A.04-30
Locality:

 

Notes:

 

 
   
 
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