Gahnite Mineral Data

Gahnite Mineral Data +

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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).

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 - HexoctahedralH-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),

Forms:

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Forms: [ 0 1 1] [ 1 1 1] [ 1 0 0]

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Crystal Structure:

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Andreozzi G B , Lucchesi S , Skogby H , Della Giusta A , European Journal of Mineralogy , 13 (2001) p.391-402, Compositional dependence of cation distribution in some synthetic, (Mg,Zn)(Al,Fe)2O4 spinels, Sample: Gah1a/a

View Additional jPOWD Structure files for Gahnite
[1] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [2] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29] [3] [30] [31] [32] [33] [34] [35] [36] [37] [38] [39] [4] [40] [41] [42] [43] [44] [45] [46] [47] [48] [49] [5] [50] [51] [52] [53] [54] [55] [56] [57] [58] [59] [6] [60] [61] [62] [63] [64] [65] [66] [67] [68] [69] [7] [70] [71] [72] [73] [74] [75] [76] [8] [9]

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

Diaphaniety:

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:

None.

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

Optical Data:

Isotropic, n=1.82.

Calculated Properties of Gahnite

Electron Density:

r_electron=4.13 gm/cc
note: r_Gahnite=4.30 gm/cc.

Fermion Index

Fermion Index = 0.01478
Boson Index = 0.98522

Photoelectric:

PE_Gahnite= 18.63 barns/electron
U=PE_Gahnite x r_electron= 76.89 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Gahnite is Not Radioactive

Gahnite Classification

Dana Class:

7.2.1.4 (7)Multiple Oxides

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

(7.2.1)(Aluminum subgroup)

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

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

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

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

Strunz Class:

IV/B.01-40 IV - Oxides

IV/B - Oxides with metal : oxygen = 3:4 (spinel type M3O4 and related), Aluminat-Spinels

IV/B.01 - Spinel group, Spinel - Gahnite series

IV/B.01-10 Spinel MgAl2O4 F d3m 4/m 3 2/m

IV/B.01-20 Hercynite FeAl2O4 F d3m 4/m 3 2/m

IV/B.01-30 Galaxite (Mn,Mg)(Al,Fe)2O4 F d3m 4/m 3 2/m

IV/B.01-40 Gahnite ZnAl2O4 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: 7.2.1.4 Strunz No: IV/B.01-40
Locality:

Notes: