Tephroite Mineral Data

General Tephroite Information

Chemical Formula: Mn2SiO4 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 Empirical Formula: Mn²⁺₂(SiO₄) Environment: Contact metamorphism of manganese bearing rocks. IMA Status: Valid Species (Pre-IMA) 1823 Locality: Franklin and Sparta, New Jersey, USA. Link to MinDat.org Location Data. Name Origin: From the Greek tephros - "ash gray" for its color. Name Pronunciation: Tephroite + Pronunciation Synonym: ICSD 100433   PDF 35-748  

Tephroite Image

Images:

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

Images: Images:

Tephroite Crystallography

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

Cleavage: {010} Indistinct Color: Gray, Olive green, Bluish green, Red, Reddish brown. Density: 4.11 - 4.39, Average = 4.25 Diaphaneity: Transparent to translucent Fracture: Brittle - Conchoidal - Very brittle fracture producing small, conchoidal fragments. Habit: Granular - Generally occurs as anhedral to subhedral crystals in matrix. Habit: Massive - Granular - Common texture observed in granite and other igneous rock. Habit: Prismatic - Crystals Shaped like Slender Prisms (e.g. tourmaline). Hardness: 6.5 - Pyrite Luminescence: Non-fluorescent. Luster: Vitreous - Greasy Magnetism: Nonmagnetic Streak: gray  

Optical Properties of Tephroite

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
Ncalc = 1.82 - 1.93 Optical Data: Biaxial (+), a=1.759, b=1.797, g=1.86, bire=0.1010, 2V(Calc)=78, 2V(Meas)=60-70. Dispersion none. Pleochroism (x): pale amber. Pleochroism (y): orange yellow.  

Calculated Properties of Tephroite

Electron Density: Bulk Density (Electron Density)=4.04 gm/cc
note: Specific Gravity of Tephroite =4.25 gm/cc.
Fermion Index: Fermion Index = 0.0066464499
Boson Index = 0.9933535501 Photoelectric: PE_Tephroite = 14.67 barns/electron
U=PE_Tephroite x rElectron Density= 59.28 barns/cc.
Radioactivity: GRapi = 0 (Gamma Ray American Petroleum Institute Units)
Tephroite is Not Radioactive  

Tephroite Classification

Dana Class: 51.03.01.04 (51)Nesosilicate Insular SiO4 Groups Only   (51.03)with all cations in octahedral [6] coordination   (51.03.01)Olivine group  

51.03.01.00 Olivine* (Mg,Fe)2SiO4 Pbnm 2/m 2/m 2/m

 

51.03.01.01 Fayalite Fe2SiO4 Pbnm 2/m 2/m 2/m

 

51.03.01.02 Forsterite Mg2SiO4 Pbnm 2/m 2/m 2/m

 

51.03.01.03 Liebenbergite (Ni,Mg)2SiO4 Pbnm 2/m 2/m 2/m

 

51.03.01.04 Tephroite Mn2SiO4 P nma 2/m 2/m 2/m

 

51.03.01.05 Laihunite FeFe2(SiO4)2 P 2₁/b 2/m

Strunz Class: 09.AC.05 09 - SILICATES (Germanates)   09.A - Nesosilicates   09.AC -Nesosilicates without additional anions;  

09.AC.05 Forsterite Mg2SiO4 Pbnm 2/m 2/m 2/m

 

09.AC.05 Glaucochroite CaMnSiO4 Pbnm 2/m 2/m 2/m

 

09.AC.05 Fayalite Fe2SiO4 Pbnm 2/m 2/m 2/m

 

09.AC.05 Olivine* (Mg,Fe)2SiO4 Pbnm 2/m 2/m 2/m

 

09.AC.05 Kirschsteinite CaFeSiO4 Pbmn 2/m 2/m 2/m

 

09.AC.05 Laihunite FeFe2(SiO4)2 P 2₁/b 2/m

 

09.AC.05 Liebenbergite (Ni,Mg)2SiO4 Pbnm 2/m 2/m 2/m

 

09.AC.05 Tephroite Mn2SiO4 P nma 2/m 2/m 2/m

 

Other Tephroite Information

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 - EUROmin Project
6 - Ecole des Mines de Paris
7 - Franklin Minerals(Dunn)
8 - Franklin Minerals(Palache)
9 - GeoScienceWorld
10 - Google Images
11 - Google Scholar
12 - Handbook of Mineralogy (MinSocAm)
13 - Handbook of Mineralogy (UofA)
14 - MinDAT
15 - Mineral and Gemstone Kingdom
16 - Mineralienatlas (Deutsch)
17 - Online Mineral Museum
18 - QUT Mineral Atlas
19 - Ruff.Info
20 - Scandinavian mineral gallery
21 - University of Colorado - Mineral Structure Data
22 - WWW-MINCRYST
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