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INVESTIGATIONS

Stone

RI min

RI max

Dens min

Dens max

Colour

Location

Info

Spectrum

UVS

UVL

Reference

Gahnite

1.793

1.794

4.4

4.589

blue

Jemaa, Nigeria

 

 

 

 

The Journal of Gemmology 1982 Vol18, N°4 p265-276

Gahnite

1.794

1.794

4.54

4.54

intense green

Brazil

 

 

 

 

Gemmologie, Zeitschrift der Deutschen Gemmologischen Gesellschaft 1996 Mar, p1

Gahnite

1.798

1.798

4.64

4.64

green

Sri Lanka

transparent

 

 

 

The Journal of Gemmology 1972 N°1, p8

Gahnite

 

 

4.74

4.74

very dark green

Barra de Salinas, Minas Gerais, Brazil

17.54ct

broad absorption below 490 and above 560, line at 515nm

inert

inert

GIA Gem Database  34280

 

TABLES

Stone

RI min

RI max

Dens min

Dens max

Reference

Gahnite

1.776

1.806

4.35

4.63

Gemmo.eu 2017

Gahnite

1.79

1.82

4.38

4.62

Tables of Gemstone Identification, Roger Dedeyne, Ivo Quintens, 2007 

Gahnite

1.791

1.818

4

4.6

Bestimmungstabellen für Edelsteine, Birgit Günther, 2008 

Gahnite

1.792

1.82

4

4.64

Gemme, Dati per l'identificazione, P. De Stefano et al, 1993 

Gahnite

1.792

1.803

4.4

4.6

Gemmological Tables, Ulrich Henn, 2004 

Gahnite

1.798

1.805

4.4

4.4

Tabellen zur Edelstein-Bestimmung, Pschichholz FGA, 1975 

Gahnite

1.798

1.8

4.4

4.64

Gems, R Webster, 5th edition 1994 

Gahnite

1.8

1.81

4

4.62

http://www.geminterest.com 

Gahnite synthetic

1.805

1.805

4.4

4.4

Bestimmungstabellen für Edelsteine, Birgit Günther, 1981 

Gahnite

1.805

1.805

4

4.62

http://www.gemmology.be 

Gahnite

1.805

1.805

4.4

4.59

Michael O'Donoghue, Gems: Their Sources, Descriptions and Identification (2006),  873pp 

Gahnite

 

 

4.4

4.4

John Sinkakas, Gemstone and mineral data book,1972 

 

CAUSE OF COLOUR

Stone

Colour

Cause of colour

Reference

Gahnite

blue

Fe²+ in octahedral coordination

Gems & Gemology Summer 1988

 

MINERAL INCLUSIONS

Inclusion

Stone

Reference

beryl

Gahnite - spinel group

The Journal of Gemmology 1982, Vol18, N°4,p265-276

columbite

Gahnite - spinel group

The Journal of Gemmology 1982, Vol18, N°4,p265-276

hematite

Gahnite - spinel group

The Journal of Gemmology 1982, Vol18, N°4,p265-276

mica

Gahnite - spinel group

The Journal of Gemmology 1982, Vol18, N°4,p265-276

zircon

Gahnite - spinel group

The Journal of Gemmology 1982, Vol18, N°4,p265-276

 

LOCALITIES

STONE

LOCALITIES

REFERENCE

Gahnite

Jemaa

Kaduna

 

Nigeria

The Journal of Gemmology 1982, Vol18, N°3, p266







 

CHEMICAL DATA  (%)