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Gahnite

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Big Photo

Franklin, Franklin Mining District, Sussex Co., New Jersey, USA
© Rob Lavinsky

Show Gahnite Photos (101)



Formula:
ZnAl
 
2
O
 
4
System:IsometricColour:Dark blue-green, yellow, ...
Lustre:VitreousHardness:7½ - 8
Member of:Spinel Group
Name:
For Swedish chemist and mineralogist, Johan Gottlieb Gahn (1745-1818).


Spinel Group, Al series. Gahnite-Hercynite Series, and the Gahnite-Spinel Series.

Classification of Gahnite

IMA status:Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
Strunz 8th edition ID:4/B.01-40
Nickel-Strunz 10th (pending) edition ID:4.BB.05

4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
B : Metal: Oxygen = 3:4 and similar
B : With only medium-sized cations
Dana 8th edition ID:7.2.1.4

7 : MULTIPLE OXIDES
2 : AB2X4
Hey's CIM Ref.:7.5.5

7 : Oxides and Hydroxides
5 : Oxides of Zn, Cd and Hg
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Type Occurrence of Gahnite

Type Locality:Falun mine, Falun, Dalarna, Sweden
Year of Discovery:1807

Physical Properties of Gahnite

Lustre:Vitreous
Colour:Dark blue-green, yellow, brown, black
Streak:Grey
Hardness (Mohs):7½ - 8
Tenacity:Brittle
Fracture:Irregular/Uneven, Conchoidal
Density (calculated):4.62 g/cm3

Crystallography of Gahnite

Crystal System:Isometric
Class (H-M):m3m (4/m 3 2/m) - Hexoctahedral
Space Group:Fd3m {F41/d 3 2/m}
Cell Parameters:a = 8.062Å
Unit Cell Volume:V 524.00 ų (Calculated from Unit Cell)
Morphology:Crystals usually octahedral.
X-Ray Powder Diffraction:
Image Loading

Radiation - Copper Kα
Data Set:
Horizontal Axis: ° to ° Vertical Axis: % Source Data: Filtered Data:
Data courtesy of RRUFF project at University of Arizona, used with permission.

Optical Data of Gahnite

Type:Isotropic

Chemical Properties of Gahnite

Formula:
ZnAl
 
2
O
 
4
Essential elements:Al, O, Zn
All elements listed in formula:Al, O, Zn
Common Impurities:Fe,Mg

Relationship of Gahnite to other Species

Series:Forms a series with Spinel (see here)
Forms a series with Hercynite (see here)
Member of:Spinel Group
Other Members of Group:

- +
Chromite
FeCr
 
2
O
 
4
Franklinite
Zn
2+
 
Fe
3+
2
O
 
4
Galaxite
(Mn,Fe,Mg)(Al,Fe)
 
2
O
 
4
Hercynite
Fe
2+
 
Al
 
2
O
 
4
Jacobsite
Mn
2+
 
Fe
3+
2
O
 
4
Magnesiochromite
MgCr
 
2
O
 
4
Magnesioferrite
MgFe
3+
2
O
 
4
Magnetite
Fe
2+
 
Fe
3+
2
O
 
4
Qandilite
(Mg,Fe)
 
2
(Ti,Fe,Al)O
 
4
Spinel
MgAl
 
2
O
 
4
Trevorite
Ni
2+
 
Fe
3+
2
O
 
4
Related Minerals - Nickel-Strunz Grouping):

- +
4.BB.05Brunogeierite
(Ge,Fe)Fe
 
2
O
 
4
4.BB.05Chromite
FeCr
 
2
O
 
4
4.BB.05Cochromite
(Co,Ni,Fe)(Cr,Al)
 
2
O
 
4
4.BB.05Coulsonite
Fe
2+
 
V
3+
2
O
 
4
4.BB.05Cuprospinel
Cu
2+
 
Fe
3+
2
O
 
4
4.BB.05Filipstadite
(Mn,Mg)
 
2
(Sb
 
.5
Fe
 
.5
)O
 
4
4.BB.05Franklinite
Zn
2+
 
Fe
3+
2
O
 
4
4.BB.05Galaxite
(Mn,Fe,Mg)(Al,Fe)
 
2
O
 
4
4.BB.05Hercynite
Fe
2+
 
Al
 
2
O
 
4
4.BB.05Jacobsite
Mn
2+
 
Fe
3+
2
O
 
4
4.BB.05Manganochromite
(Mn,Fe)(Cr,V)
 
2
O
 
4
4.BB.05Magnesiocoulsonite
MgV
 
2
O
 
4
4.BB.05Magnesiochromite
MgCr
 
2
O
 
4
4.BB.05Magnesioferrite
MgFe
3+
2
O
 
4
4.BB.05Magnetite
Fe
2+
 
Fe
3+
2
O
 
4
4.BB.05Nichromite
(Ni,Co,Fe)(Cr,Fe,Al)
 
2
O
 
4
4.BB.05Qandilite
(Mg,Fe)
 
2
(Ti,Fe,Al)O
 
4
4.BB.05Spinel
MgAl
 
2
O
 
4
4.BB.05Trevorite
Ni
2+
 
Fe
3+
2
O
 
4
4.BB.05Ulvöspinel
Fe
 
2
TiO
 
4
4.BB.05Vuorelainenite
(Mn,Fe)(V,Cr)
 
2
O
 
4
4.BB.05Zincochromite
ZnCr
 
2
O
 
4
4.BB.10Hausmannite
MnMn
 
2
O
 
4
4.BB.10Hetaerolite
ZnMn
 
2
O
 
4
4.BB.10Hydrohetaerolite
ZnMn
 
2
O
 
4
 · H
 
2
O
4.BB.10Iwakiite
Mn(Fe,Mn)
 
2
O
 
4
4.BB.15Maghemite
Fe
3+
2
O
 
3
4.BB.15Titanomaghemite
Fe
3+
 
(Fe
3+
 
,Ti
4+
 
,Fe
2+
 
,◻)
 
2
O
 
4
4.BB.20Tegengrenite
(Mg,Mn
2+
 
)
 
2
Sb
5+
0.5
(Mn
3+
 
,Si,Ti)
 
0.5
O
 
4
4.BB.25Xieite
Fe
2+
 
Cr
 
2
O
 
4
Related Minerals - Hey's Index Grouping:

- +
7.5.1Zincite
(Zn,Mn
2+
 
,Fe
2+
 
)O
7.5.2Sweetite
Zn(OH)
 
2
7.5.3Ashoverite
Zn(OH)
 
2
7.5.4Wülfingite
Zn(OH)
 
2
7.5.6Hetaerolite
ZnMn
 
2
O
 
4
7.5.7Hydrohetaerolite
ZnMn
 
2
O
 
4
 · H
 
2
O
7.5.8Chalcophanite
(Zn,Fe,Mn)Mn
 
3
O
 
7
 · 3H
 
2
O
7.5.9Woodruffite
Zn(Mn
4+
 
,Mn
3+
 
)
 
5
O
 
10
·3½H
 
2
O
7.5.10Franklinite
Zn
2+
 
Fe
3+
2
O
 
4
7.5.11Monteponite
CdO
7.5.12Montroydite
HgO

Other Names for Gahnite

Synonyms:
AutomaliteAutomoliteAutomolithDysluiteFahlunite (of Karsten)
Gahnite (of von Moll)Spinellus superiusZinc Spinel
Other Languages:
French:Spinelle Zincifère
German:Gahnit
Automalit
Automolit
Zinkspinell
Italian:Gahnite
Portuguese:Gahnita
Russian:Ганит
Spanish:Automalita
Automolita
Gahnita
Varieties:
KreittoniteLimaiteManganoan Gahnite

Other Information

Health Warning:No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for Gahnite

Reference List:

- +
Palache, Charles, Harry Berman & Clifford Frondel (1944), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana Yale University 1837-1892, Seventh edition, Volume I: 689-697.

Mineralogical Magazine: 62: 41-54.

Spry, P.G. (1987) Compositional zoning in zincian spinel. Canadian Mineralogist: 25: 97-104.

Waerenborgh, J.C., Annersten, H., Ericsson, T., Figueiredo, M.O., and Cabral, J.M.P. (1990) A Mössbauer study of natural gahnite spinels showing strongly temperature dependent quadrupole splitting distributions. European Journal of Mineralogy: 2: 267-271.

O'Neill, H.St.C. and Dollase, W.A. (1994) Crystal structures and cation distribution in simple spinels from powder XRD structural refinements: MgCr2O4, ZnCr2O4, Fe3O4, and the temperature dependence of the cation distribution in ZnAl2O4. Physics and Chemistry of Minerals: 20: 541-555.

Mindat.org articles about Gahnite

Article entries:
The Often Overlooked Broken Hill GahnitesTrevor Dart

Internet Links for Gahnite

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  • Raman and XRD data at RRUFF project
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    Locality Updated: Chester, Windsor Co., Vermont, USAFrom Peter Cristofono, 9th Feb 2012 23:36:38