Gahnite Mineral Data

General Gahnite Information

Chemical Formula:

ZnAl2O4

Composition:

Molecular Weight = 183.35 gm

Aluminum 29.43 % Al 55.61 % Al₂O₃

Zinc 35.66 % Zn 44.39 % ZnO

Oxygen 34.90 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

ZnAl₂O₄

Environment:

Metamorphic and pegmatitic rocks.

IMA Status:

Valid Species (Pre-IMA) 1807

Locality:

Falun, Sweden. Link to MinDat.org Location Data.

Name Origin:

Named after the Swedish chemist and mineralogist, J. G. Gahn (1745-1818).

Name Pronunciation:

Gahnite

Synonym:

ICSD 9559

PDF 5-669

Zinc Spinal

Gahnite Image

Images:

Gahnite

Comments: Deep blue octahedral crystals of gahnite in quartz.
Location: Franklin, Sussex County, New Jersey, USA. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Images:

Gahnite

Comments: Optical micrograph of gahnite (blue) + Na-Ca-Li mica pseudomorph after staurolite in calcite matrix pigmented with brownish Fe-(hydr)oxide. (AmMin, 88:794).
Location: Diaspore-bearing metabauxite from East Samos (Greece). Scale: See Image.
© American Mineralogist

Gahnite Crystallography

Cell Dimensions:

a = 8.062, Z = 8; V = 524.00 Den(Calc)= 4.65

Crystal System:

Isometric - Hexoctahedral H-M Symbol (4/m 3 2/m) Space Group: F d3m

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

By Intensity(I/I_o): 2.438(1), 2.861(0.84), 1.429(0.43),

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

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Physical Properties of Gahnite

Cleavage:

{111} Indistinct

Color:

Bluish green, Grayish green, Deep leek green, Greenish black, Bluish black.

Density:

4 - 4.6, Average = 4.3

Diaphaneity:

Subtransparent to opaque

Fracture:

Uneven - Flat surfaces (not cleavage) fractured in an uneven pattern.

Habit:

Euhedral Crystals - Occurs as well-formed crystals showing good external form.

Habit:

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

Habit:

Striated - Parallel lines on crystal surface or cleavage face.

Hardness:

8 - Topaz

Luminescence:

Non-fluorescent.

Luster:

Vitreous (Glassy)

Magnetism:

Nonmagnetic

Streak:

gray

Optical Properties of Gahnite

Gladstone-Dale:

CI meas= -0.029 (Excellent) - where the CI = (1-KPDmeas/KC)
CI calc= 0.048 (Good) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.1763,KPDmeas= 0.1907,KC= 0.1852
Ncalc = 1.74 - 1.86

Optical Data:

Isotropic, n=1.82.

Calculated Properties of Gahnite

Electron Density:

Bulk Density (Electron Density)=4.13 gm/cc
note: Specific Gravity of Gahnite =4.30 gm/cc.

Fermion Index:

Fermion Index = 0.01
Boson Index = 0.99

Photoelectric:

PE_Gahnite= 18.63 barns/electron
U=PE_Gahnite x rElectron Density= 76.89 barns/cc.

Radioactivity:

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

Gahnite Classification

Dana Class:

07.02.01.04 (07)Multiple Oxides

(07.02)(A+ B++)2 X4 Spinel group

(07.02.01)(Aluminum subgroup)

07.02.01.01 Spinel MgAl2O4 F d3m 4/m 3 2/m

07.02.01.02 Galaxite (Mn,Mg)(Al,Fe)2O4 F d3m 4/m 3 2/m

07.02.01.03 Hercynite FeAl2O4 F d3m 4/m 3 2/m

07.02.01.04 Gahnite ZnAl2O4 F d3m 4/m 3 2/m

Strunz Class:

04.BB.05 04 - OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodate

04.B - Metal:Oxygen = 3:4 and similar

04.BB -With only medium-sized cations

04.BB.05 Cochromite (Co,Ni,Fe)(Cr,Al)2O4 F d3m 4/m 3 2/m

04.BB.05 Filipstadite (Mn,Mg)4SbFeO8 pseudo ISO 2/m 2/m 2/m

04.BB.05 Magnetite FeFe2O4 F d3m 4/m 3 2/m

04.BB.05 Gahnite ZnAl2O4 F d3m 4/m 3 2/m

04.BB.05 Chromite FeCr2O4 F d3m 4/m 3 2/m

04.BB.05 Galaxite (Mn,Mg)(Al,Fe)2O4 F d3m 4/m 3 2/m

04.BB.05 Cuprospinel (Cu,Mg)Fe2O4 F d3m 4/m 3 2/m

04.BB.05 Donathite? (Fe,Mg)(Cr,Fe)2O4 P 4/nnm 4/m 2/m 2/m

04.BB.05 Brunogeierite (Ge,Fe)Fe2O4 F d3m 4/m 3 2/m

04.BB.05 Coulsonite FeV2O4 F d3m 4/m 3 2/m

04.BB.05 Hercynite FeAl2O4 F d3m 4/m 3 2/m

04.BB.05 Franklinite (Zn,Mn,Fe)(Fe,Mn)2O4 F d3m 4/m 3 2/m

04.BB.05 Jacobsite (Mn,Fe,Mg)(Fe,Mn)2O4 F d3m 4/m 3 2/m

04.BB.05 Magnesiochromite MgCr2O4 F d3m 4/m 3 2/m

04.BB.05 Magnesioferrite MgFe2O4 F d3m 4/m 3 2/m

04.BB.05 Magnesiocoulsonite MgV2O4 F d3m 4/m 3 2/m

04.BB.05 Manganochromite (Mn,Fe)(Cr,V)2O4 F d3m 4/m 3 2/m

04.BB.05 Qandilite (Mg,Fe)2(Ti,Fe,Al)O4 F d3m 4/m 3 2/m

04.BB.05 Nichromite (Ni,Co,Fe)(Cr,Fe,Al)2O4 F d3m 4/m 3 2/m

04.BB.05 Spinel MgAl2O4 F d3m 4/m 3 2/m

04.BB.05 Ulvospinel TiFe2O4 F d3m 4/m 3 2/m

04.BB.05 Zincochromite ZnCr2O4 F d3m 4/m 3 2/m

04.BB.05 Trevorite NiFe2O4 F d3m 4/m 3 2/m

04.BB.05 Vuorelainenite (Mn,Fe)(V,Cr)2O4 F d3m 4/m 3 2/m

Other Gahnite Information

References:

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

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Gahnite

ZnAl2O4
Dana No: 07.02.01.04 Strunz No: 04.BB.05
Locality:

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