Eudidymite Mineral Data

General Eudidymite Information

Chemical Formula:

NaBeSi3O7(OH)

Composition:

Molecular Weight = 245.26 gm

Sodium 9.37 % Na 12.64 % Na₂O

Beryllium 3.67 % Be 10.20 % BeO

Silicon 34.35 % Si 73.49 % SiO₂

Hydrogen 0.41 % H 3.67 % H₂O

Oxygen 52.19 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

NaBe(Si₃O₇)(OH)

Environment:

A late-stage mineral in alkalic nepheline syenite pegmatites.

IMA Status:

Valid Species (Pre-IMA) 1887

Locality:

Island Ovre-Aro, Langesundfiord, Norway. Link to MinDat.org Location Data.

Name Origin:

From the Greek for well and twinned, in allusion to its common occurrence in twins.

Name Pronunciation:

Eudidymite + Pronunciation

Synonym:

ICSD 26001

PDF 14-201

Eudidymite Image

Images:

Eudidymite Epididymite

Comments: Translucent prismatic crystals of eudidymite on white opaque epididymite.
Location: Narsaarsuk, Greenland. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Eudidymite Crystallography

Axial Ratios:

a:b:c =1.7127:1:1.8997

Cell Dimensions:

a = 12.64, b = 7.38, c = 14.02, Z = 8; beta = 103.7° V = 1,270.62 Den(Calc)= 2.56

Crystal System:

Monoclinic - Prismatic H-M Symbol (2/m) Space Group: C 2/c

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

By Intensity(I/I_o): 3.163(1), 3.074(0.8), 3.398(0.8),

Physical Properties of Eudidymite

Cleavage:

{001} Good, {551} Good

Color:

Blue, Colorless, Violet, Gray, Yellow.

Density:

2.553

Diaphaneity:

Transparent to translucent

Fracture:

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

Habit:

Tabular - Form dimensions are thin in one direction.

Habit:

Twinning Common - Crystals are usually twinned.

Hardness:

6 - Orthoclase

Luster:

Vitreous (Glassy)

Streak:

white

Optical Properties of Eudidymite

Gladstone-Dale:

CI meas= -0.003 (Superior) - where the CI = (1-KPDmeas/KC)
CI calc= 0 (Superior) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2138,KPDmeas= 0.2144,KC= 0.2138
Ncalc = 1.55

Optical Data:

Biaxial (+), a=1.545, b=1.546, g=1.551, bire=0.0060, 2V(Calc)=50, 2V(Meas)=30. Dispersion r > v distinct.

Pleochroism (x):

colorless.

Pleochroism (y):

colorless.

Pleochroism (z):

colorless.

Calculated Properties of Eudidymite

Electron Density:

Bulk Density (Electron Density)=2.55 gm/cc
note: Specific Gravity of Eudidymite =2.56 gm/cc.

Fermion Index:

Fermion Index = 0.05
Boson Index = 0.95

Photoelectric:

PE_Eudidymite= 1.51 barns/electron
U=PE_Eudidymite x rElectron Density= 3.85 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)
Eudidymite is Not Radioactive

Eudidymite Classification

Dana Class:

66.03.01.03 (66)Inosilicate Double-Width Unbranched Chains, W=2

(66.03)with chains P>2

(66.03.01)P=3

66.03.01.01 Xonotlite Ca6Si6O17(OH)2 P 2/a 2/m

66.03.01.02 Zorite Na6Ti5[Si12O34](O,OH)5•11(H2O) C mmm 2/m 2/m 2/m

66.03.01.03 Eudidymite NaBeSi3O7(OH) C 2/c 2/m

66.03.01.04 Epididymite NaBeSi3O7(OH) Pnam 2/m 2/m 2/m

66.03.01.05 Yuksporite (Sr,Ba)2K4(Ca,Na)14([],Mn,Fe){(Ti,Nb)4(O,OH)4[Si6O17]2[Si2O7]3}(H2O,OH)n,n~3 P 2₁/m 2/m

66.03.01.06 Haineaultite! (Na,Ca)5Ca(Ti,Nb)5(Si,S)12O34(OH,F)8•5(H2O) C 222 2 2 2

66.03.01.07 Chivruaiite! Ca4(Ti,Nb)5[(Si6O17)2[(OH,O)5]•13-14H2O C mmm 2/m 2/m 2/m

Strunz Class:

09.DG.60 09 - SILICATES (Germanates)

09.D - Inosilicates* Structural terminology according to Liebau (1985)

09.DG -Inosilicates with 3-periodic single and multiple chains

09.DG.60 Eudidymite NaBeSi3O7(OH) C 2/c 2/m

Other Eudidymite Information

References:

NAME( AntBidBlaNic2) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Ford32)

See Also:

Links to other databases for Eudidymite :
1 - Alkali-Nuts(English)
2 - Alkali-Nuts(Francais)
3 - Am. Min. Crystal Structure Database
4 - Amethyst Galleries' Mineral Gallery
5 - Athena
6 - EUROmin Project
7 - Ecole des Mines de Paris
8 - GeoScienceWorld
9 - Google Images
10 - Google Scholar
11 - Handbook of Mineralogy (MinSocAm)
12 - Handbook of Mineralogy (UofA)
13 - MinDAT
14 - Mineralienatlas (Deutsch)
15 - Online Mineral Museum
16 - QUT Mineral Atlas
17 - Ruff.Info
18 - WWW-MINCRYST

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Eudidymite

NaBeSi3O7(OH)
Dana No: 66.03.01.03 Strunz No: 09.DG.60
Locality:

Notes:

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