Thortveitite Mineral Data

Thortveitite Mineral Data +

General Thortveitite Information

Chemical Formula:

(Sc,Y)2Si2O7

Composition:

Molecular Weight = 280.05 gm

Yttrium 15.87 % Y 20.16 % Y₂O₃

Scandium 24.08 % Sc 36.93 % Sc₂O₃

Silicon 20.06 % Si 42.91 % SiO₂

Oxygen 39.99 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

Sc_1.5Y_0.5Si₂O₇

Environment:

Granitic pegmatite rocks.

IMA Status:

Valid Species (Pre-IMA) 1911

Locality:

Iveland, Setesdal, Norway. Link to MinDat.org Location Data.

Name Origin:

Named after the Norwegian engineer, O. Thortveit.

Synonym:

ICSD 75925

PDF 20-1037

Thortveitite Image

Images:

Thortveitite

Comments: Small white prismatic crystals of thortveitite on matrix.
Location: A4 highway tunnel, Thiemendorf, K?nigshain, Oberlausitz, Saxony, Germany. Scale: Picture size 1.7 mm.
© Thomas Witzke / Abraxas-Verlag

Thortveitite Crystallography

Axial Ratios:

a:b:c =0.7706:1:0.5493

Cell Dimensions:

a = 6.587, b = 8.547, c = 4.695, Z = 2; beta = 102.65° V = 257.91 Den(Calc)= 3.61

Crystal System:

Monoclinic - PrismaticH-M Symbol (2/m) Space Group: C 2/m

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

By Intensity(I/I_o): 3.11(1), 3.13(1), 2.93(0.45),

Crystal Structure:

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Bianchi R , Pilati T , Diella V , Gamaccioli C M , Mannucci G , American Mineralogist , 73 (1988) p.601-607, A re-examination of thortveitite, Sample 1 from Iveland

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

Physical Properties of Thortveitite

Cleavage:

[100] Perfect

Color:

Brown, Grayish black, Black, Grayish green.

Density:

3.5

Diaphaniety:

Translucent to opaque

Fracture:

Conchoidal - Fractures developed in brittle materials characterized by smoothly curving surfaces, (e.g. quartz).

Habit:

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

Habit:

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

Habit:

Radial - Crystals radiate from a center without producing stellar forms (e.g. stibnite)

Hardness:

6.5 - Pyrite

Luminescence:

Non-fluorescent.

Luster:

Vitreous - Adamantine

Streak:

gray

Optical Properties of Thortveitite

Gladstone-Dale:

CI meas= -0.028 (Excellent) - where the CI = (1-KPDmeas/KC)
CI calc= 0.003 (Superior) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2177,KPDmeas= 0.2246,KC= 0.2184

Optical Data:

Biaxial (-), a=1.756, b=1.793, g=1.809, bire=0.0530, 2V(Calc)=64, 2V(Meas)=65.

Pleochroism (x):

deep green.

Pleochroism (y):

brownish yellow.

Pleochroism (z):

brownish yellow.

Calculated Properties of Thortveitite

Electron Density:

r_electron=3.48 gm/cc
note: r_Thortveitite=3.61 gm/cc.

Fermion Index

Fermion Index = 0.00955
Boson Index = 0.99045

Photoelectric:

PE_Thortveitite= 23.53 barns/electron
U=PE_Thortveitite x r_electron= 81.90 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Thortveitite is Not Radioactive

Thortveitite Classification

Dana Class:

55.2.1a.4 (55)Sorosilicate Si2O7 Groups, Generally with No Additional Anions

(55.2)with cations in [6] coordination

(55.2.1a)Thortveitite group

55.2.1a.1 Gittinsite CaZrSi2O7 C 2/m 2/m

55.2.1a.2 Keiviite-(Y) (Y,Yb)2Si2O7 C 2/m 2/m

55.2.1a.3 Keiviite-(Yb) (Yb,Y)2Si2O7 C 2/m 2/m

55.2.1a.4 Thortveitite (Sc,Y)2Si2O7 C 2/m 2/m

Strunz Class:

VIII/C.01-10 VIII - Silicates

VIII/C - Sorosilicates, with [Si2O7]6-, without anions unfamiliar to tetraheders

VIII/C.01 - Thortveitite - Rowlandite-(Y) series

VIII/C.01-10 Thortveitite (Sc,Y)2Si2O7 C 2/m 2/m

VIII/C.01-15 Gittinsite CaZrSi2O7 C 2/m 2/m

VIII/C.01-18 Kristiansenite! Ca2ScSn(Si2O7)(Si2O6OH) C1 1

VIII/C.01-20 Keiviite-(Y) (Y,Yb)2Si2O7 C 2/m 2/m

VIII/C.01-30 Keiviite-(Yb) (Yb,Y)2Si2O7 C 2/m 2/m

VIII/C.01-40 Yttrialite-(Y) (Y,Th)2Si2O7 P 2₁/m 2/m

VIII/C.01-45 Percleveite-(Ce)! (Ce,La,Nd)2Si2O7 P 4₁ 4

VIII/C.01-50 Rowlandite-(Y) Y4FeSi4O14F2(?) None

Other Thortveitite Information

References:

NAME( Duda&Rejl90) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Ford32)

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Thortveitite

(Sc,Y)2Si2O7
Dana No: 55.2.1a.4 Strunz No: VIII/C.01-10
Locality:

Notes: