Nepheline Mineral Data

General Nepheline Information

Chemical Formula:

(Na,K)AlSiO4

Composition:

Molecular Weight = 146.08 gm

Potassium 6.69 % K 8.06 % K₂O

Sodium 11.80 % Na 15.91 % Na₂O

Aluminum 18.47 % Al 34.90 % Al₂O₃

Silicon 19.23 % Si 41.13 % SiO₂

Oxygen 43.81 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

Na_0.75K_0.25Al(SiO₄)

Environment:

Silica-poor igneous rocks.

IMA Status:

Valid Species (Pre-IMA) 1800

Locality:

Magnet Cove, Magnet Cove, Ouachita Mountains, Hot Spring County, Arkansas, USA. Link to MinDat.org Location Data.

Name Origin:

From the Greek nephele, "cloud," because it becomes clouded when put in strong acid.

Name Pronunciation:

Nepheline + Pronunciation

Synonym:

Elaeolite

ICSD 2937

Nephelite

PDF 9-338

Nepheline Image

Images:

Nepheline

Comments: Stubby, hexagonal prism of Nepheline in matrix.
Location: Point of Rocks Mesa, Colfax County, New Mexico. Scale: Not Given.
© Lou Perloff / Photo Atlas of Minerals

Nepheline Crystallography

Axial Ratios:

a:c = 1:0.83966

Cell Dimensions:

a = 10.01, c = 8.405, Z = 8; V = 729.35 Den(Calc)= 2.66

Crystal System:

Hexagonal - Pyramidal H-M Symbol (6) Space Group: P 6₃

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

By Intensity(I/I_o): 3.069(1), 4.25(0.75), 4.015(0.7),

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Forms: ( 0 1 0) ( 0 0 1)

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Physical Properties of Nepheline

Cleavage:

{1010} Poor

Color:

White, Gray, Brown, Brownish gray, Reddish white.

Density:

2.55 - 2.65, Average = 2.59

Diaphaneity:

Transparent to translucent to opaque

Fracture:

Sub Conchoidal - Fractures developed in brittle materials characterized by semi-curving surfaces.

Habit:

Massive - Granular - Common texture observed in granite and other igneous rock.

Habit:

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

Hardness:

6 - Orthoclase

Luminescence:

Non-fluorescent.

Luster:

Vitreous - Greasy

Streak:

white

Optical Properties of Nepheline

Dichroism (e):

colorless.

Dichroism (w):

turbid gray.

Gladstone-Dale:

CI meas= -0.015 (Superior) - where the CI = (1-KPDmeas/KC)
CI calc= 0.008 (Superior) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2023,KPDmeas= 0.2069,KC= 0.2038
Ncalc = 1.52 - 1.54

Optical Data:

Uniaxial (-), e=1.528-1.544, w=1.531-1.549, bire=0.0030-0.0050.

Calculated Properties of Nepheline

Electron Density:

Bulk Density (Electron Density)=2.62 gm/cc
note: Specific Gravity of Nepheline =2.66 gm/cc.

Fermion Index:

Fermion Index = 0.0091968132
Boson Index = 0.9908031868

Photoelectric:

PE_Nepheline= 2.13 barns/electron
U=PE_Nepheline x r_electron= 5.59 barns/cc.

Radioactivity:

GRapi = 95.15 (Gamma Ray American Petroleum Institute Units)
Concentration of Nepheline per GRapi unit = 1.05 (%)

Estimated Radioactivity from Nepheline - barely detectable

Nepheline Classification

Dana Class:

76.02.01.02 (76)Tectosilicate Al-Si Framework

(76.02)Feldspathoids and related species

(76.02.01)Nepheline group

76.02.01.01 Kalsilite KAlSiO4 P 3₁c 3m

76.02.01.02 Nepheline (Na,K)AlSiO4 P 6₃ 6

76.02.01.03 Trikalsilite (K,Na)AlSiO4 P 6₃ 6

76.02.01.04 Panunzite (K,Na)AlSiO4 P 6₃ 6

76.02.01.05 Kaliophilite KAlSiO4 P 6₃22 6 2 2

76.02.01.06 Yoshiokaite (Ca8-(x/2)[](x/2)Al16-xSixO32) P 3 3

76.02.01.07 Megakalsilite! KAlSiO4 P 6₃ 6

Strunz Class:

09.FA.05 09 - SILICATES (Germanates)

09.F - Tektosilicates without Zeolitic H2O

09.FA -Tektosilicates without additional non-tetrahedral anions, (Al,B):Si = 1:1

09.FA.05 Nepheline (Na,K)AlSiO4 P 6₃ 6

09.FA.05 Kaliophilite KAlSiO4 P 6₃22 6 2 2

09.FA.05 Kalsilite KAlSiO4 P 3₁c 3m

09.FA.05 Panunzite (K,Na)AlSiO4 P 6₃ 6

09.FA.05 Trikalsilite (K,Na)AlSiO4 P 6₃ 6

09.FA.05 Megakalsilite! KAlSiO4 P 6₃ 6

09.FA.05 Yoshiokaite (Ca8-(x/2)[](x/2)Al16-xSixO32) P 3 3

Other Nepheline Information

References:

NAME( Sinkankas66) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Mason68)

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Nepheline

(Na,K)AlSiO4
Dana No: 76.02.01.02 Strunz No: 09.FA.05
Locality:

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