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INVESTIGATIONS

Stone

RI min

RI max

Dens min

Dens max

Colour

Location

Info

Spectrum

UVS

UVL

Reference

Tortoise shell

1.54

1.54

1.26

1.35

 

 

aggregate-like under crossed polarisers; from the hawkshill turtle and rarely the green turtle

 

 

chalky blue-white (light areas), dark parts appear brown

Gems & Gemology 2006 spring p36-52

Tortoise shell

1.56

1.56

 

 

orange with brown patches

 

a scepter of laminated tortoise shell, hot point test: burned protein

 

blue

strong blue

Gems & Gemology 2016 Winter, p419-420

 

TABLES

Stone

RI min

RI max

Dens min

Dens max

Reference

Tortoise shell

1.53

1.586

1.26

1.35

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

Tortoise shell

1.54

1.54

1.26

1.35

John Sinkakas, Gemstone and mineral data book,1972 

Tortoise shell

1.54

1.56

1.26

1.35

http://www.geminterest.com 

Tortoise shell

1.54

1.54

1.26

1.35

Gems, R Webster, 5th edition 1994 

Tortoise shell

1.54

1.56

1.26

1.35

Gemology Tools Professional 2010

Tortoise shell

1.54

1.56

1.25

1.31

Gemmo.eu 2017

Tortoise shell

1.55

1.55

1.29

1.29

Gemmological Tables, Ulrich Henn, 2004 

 

CAUSE OF COLOUR

Stone

Colour

Cause of colour

Reference

Tortoise shell

yellow to brown

charge transfer in organic products

Gems & Gemology Summer 1988

 

CHEMICAL DATA (%)