Gems & Gemological Institute of Pakistan(GGIP ... - Gemology Online

Gems & Gemological Institute 

of Pakistan(GGIP)-Peshawar. 

1

Separa&on of Natural Blue Spinel Colored by Cobalt from 

imita&on/synthe&c gemstones with the help of color filters/ 

Ultraviolet Lamp 

OR 

The effect of Blue stones colored by cobalt in Colored filters and 

in UV (Long wave/short wave) 

Presented to my best Japanese friend 

Akira Kono 

CEO of SERAPH & Co. Izumi, Osaka, Japan. 

Reported and prepared by Hamid Usman KhaIak (HUK)-‐AG Gemologist 

Gems and Gemological Ins&tute of Pakistan (GGIP)-‐Peshawar. 

9/23/12 

Gems & Gemological Institute of 

Pakistan-Peshawar. 

2

Separa&on of Natural Blue Spinel Colored by Cobalt from imita&on/synthe&c gemstones with the 

help of color filters/ Ultraviolet Lamp 

OR 

The effect of Blue stones colored by cobalt in Colored filters and in UV (Long wave/short wave) 

} Introduc&on 

} Blue spinel colored by cobalt is reported in Vietnams, Hunza valley 

Pakistan and in Sri lanka. 

} Cobalt is a lustrous grayish silvery metal. It is very hard and can 

take very good polish. 

} Cobalt is also ferromagne&c and therefore is capable of being 

magne&zed. 

} Cobalt is a transi&on element and when it found in minerals or in 

gemstone in traces it produce two type of colors 

} 1.Blue 2. Pink. 

} Blue mineral and gemstone due to Cobalt are Lusakite and Blue 

spinel. 

} Pink minerals due to cobalt are Erythrite, roselite, spherocobal&te. 

9/23/12 



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Separa&on of Natural Blue Spinel Colored by Cobalt from imita&on/synthe&c gemstones with the 

help of color filters/ Ultraviolet Lamp 

OR 

The effect of Blue stones colored by cobalt in Colored filters and in UV (Long wave/short wave) 

Aim of the introduc&on of new test in Gemology: 

The objec&ves of the introduc&on of this test are 

• to iden&fy the gemstones through a sample instrument 

(advanced gemological instruments are very expensive and 

their prices may be equivalent to GGIP fund). 

• To introduced quick iden&fica&ons methods to save the 

precious &me (easily separate blue spinel from blue stone lot) 

• Promote the using of sample gemology tes&ng tools which 

are easily available and affordable. 

• To promote an easy gemstones iden&fica&on methods which 

can handle easily a common trade people. 

9/23/12 



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9/23/12 

Test Details 

• Details of the conduct test : For carry out this 

test I selected 10 cut and polished blue 

stones( glass and spinel) of different tone and 

saturaMon. Due to unavailability of cut blue 

spinel I selected one number of blue spinel 

specimen , locality Hunza , Pakistan. 



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imita&on/synthe&c gemstones with the help of color filters. 

Different tone and saturation synthetic spinel colored by cobalt. 



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Different tone and saturation Glass(Paste) colored by cobalt. 



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Natural Blue spinel colored by cobalt specimen . Many spinel 

crystals can be seen embedded in the calcite . 



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The selected gemstones for testing 

From left to right, first five are blue glass colored by cobalt then in middle one is 

Natural spinel colored by cobalt specimen and other five stones are 

Synthetic spinel colored by cobalt. 



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Tools need for this test 

1. To carried out this test we needs 

two types of filters and strong 

over head light (tungsten light is 

preferable) and white back ground. 

2. Ultraviolet lamp with capability of Long 

waves(LW) and short waves (SW), 

Black background. 

• 



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SeparaMon of Natural Blue Spinel Colored by Cobalt from imitaMon/ 

syntheMc gemstones with the help of color filters 

• Filters which we needs: The filters are divided 

into two category 

1. OpMonal filters 2. Compulsory filter. 

1. OpMonal filters : op&onal filters means that 

availability of any one filter is enough for this 

test. 

2. Compulsory filter. Compulsory filters means 

that without availability of this filter we can 

not do this test. 



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9/23/12 

SeparaMon of Natural Blue Spinel Colored by Cobalt from imitaMon/syntheMc 

gemstones with the help of color filters 

• 1. OpMonal filters 

• In op&onal filters we are required any one of the 

following filters 1.Chelsea filter 2.Aqua filter 3. 

SyntheMc Emerald filter(The described three filters gives the same 

result) 

• 2. Compulsory filter. 

• For this test the Synthe&c Emerald support filter 

is considered a compulsory filter. 



12

9/23/12 

SeparaMon of Natural Blue Spinel Colored by Cobalt from 

imitaMon/syntheMc gemstones with the help of color filters 



Optional filters and Compulsory 

filter. 

Chelsea , Aqua and synthetic Emerald 

filter are optional filters 

and 

Synthetic support Emerald filter is 

Compulsory filter. 

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9/23/12 


syntheMc gemstones with the help of color filters 

• TesMng Procedure: placed the stones on white 

background under the strong over head light 

and see through the filters 

• Effect in opMonal filters: All the stones turn to 

red. 

• Effect in compulsory filter: on viewing through 

the Synthe&c Emerald support filter I obtained 

the following result 



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Separa&on of Natural Blue Spinel Colored by Cobalt from imita&on/synthe&c 


• All the glass of different tone and saturaMon do not 

changes its color 

• Natural blue spinel colored by cobalt turn into 

strong red. 

• SyntheMc spinel colored by cobalt stone turn its 

color into Pale color and on stone turn it color in 

very light reddish shade. 

9/23/12 



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optional filters 

9/23/12 

op&onal filters 

1. Effect in Chelsea Color Filter (CCF) 

In Chelsea filter all the stones turns to red. 

Separation of Natural Blue Spinel Colored by Cobalt from imitation/synthetic 




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2. Effect in Aqua Color Filter 



In Aqua filter all the stones turns to red. 

Same result as Chelsea filter. 

Separation of Natural Blue Spinel Colored by Cobalt from imitation/synthetic 


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2. Effect in Synthe&c Emerald color filter. 

In Synthetic Emerald filter all the stones turns to red. 

Same result as Chelsea filter and Aqua filter 

Separation of Natural Blue Spinel Gems Colored & Gemological by Cobalt Institute from of imitation/synthetic gemstones 

9/23/12 

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with the help of color filters 

Pakistan-Peshawar.

Compulsory filter 


Effect in Synthe&c Support Emerald Filter. 

1. Glass do not changes its color 

2. Natural blue spinel colored by cobalt turn into strong red. 

3. Synthetic spinel color by cobalt turn its color into Pale color 

and one stone turn it color into very light red shade or Pastel red color. 


Separation 9/23/12 of Natural Blue Spinel Colored by Cobalt 19 


from imitation/synthetic gemstones with the help of color 

filters

9/23/12 



From left to right Rectangular cut syn.spinel 

Turn it color into very light red and the other two 

Syn. Spinel stones looks pale color. 



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Same stones but with different background 

From left to right Rectangular cut syn.spinel 

Turn it color into very light red and the other two 

Syn. Spinel stones looks pale color. 



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Dark color Syn. Spinel in Compulsory filter 



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Natural Spinel specimen in Syn. Support Emerald Filter 

In syn. support Emerald Filter Natural spinel turns its color 

Into strong Red. 



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syntheMc gemstones with the help of color filters. 

Summary of the effect of Blue stones colored by cobalt 

in Colored filters. 

S# Gems Effect in OpMonal 

filters 

(Chelsea, Aqua, 

SyntheMc Emerald 

filter) 



Effect in 


(syntheMc Emerald 

support filter) 

comments 

Nat. Blue Spinel Red Red In all the 

men&oned look 

red 

SyntheMc Blue Spinel Red Pale to Very light 

red 

Blue Glass Red Inert 

Some stones turns 

to pale color and 

one stone turn to 

very light red &nt 

color. 

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9/23/12 

The effect of Blue stones colored by cobalt in Colored filters 

and in UV (Long wave/short wave) 

• TesMng Procedure: placed the stones on black 

background and note stone's reac&on in the type 

of radia&on used -‐ whether long waves or short 

waves. 

• Effect in Long waves: In long waves the blue glass 

show no change (inert), Natural spinel turn to red 

and syn. Spinel also turn to red. 

• Effect in Short waves. In short waves the blue 

glass turns to chalky, Natural spinel show no 

change (Inert)and syn. Spinel turn to chalky. 



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The effect of Blue stones colored by cobalt in Colored filters and in 

UV (Long wave/short wave) 

Summary of the effect of Blue stones colored by cobalt in 

Long waves/Short waves 

S# Gems Effect in LW Effect in SW Comments 

1 Nat. Blue Spinel Red Inert 

2 SyntheMc Blue Spinel Red Chalky Light color stones strong 

chalky in SW as 

compared to intense color 

stones 

3 Blue Glass Inert Two type effect 

1. Majority Chalky 

2. Yellowish color 

9/23/12 



It is observed that the 

glass which show 

yellowish color in SW 

have magne&c property., 

weak to moderate. But 

blue glass show chalky 

effect in SW have no 

magne&c property. 

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Effect in Long waves/Short waves 

In Short waves blue glass colored by cobalt turns into two types 

1. Chalky (mostly) just like Syn.spinel 

2. Turn into yellow color and this type glass show magnetic property weak to 

moderate. 



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In Long waves syn. Spinel colored by 

cobalt turns to Red 

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In short waves syn. Spinel colored by 

Cobalt turn into Chalky 

Note: The syn. Spinel which body color is 

Light blue shows strong chalky effect as 

Compared to dark color syn. Spinel. 

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Natural spinel colored by in Long waves 

In Long waves Natural spinel colored by cobalt turns into strong red 

But in short waves it show inter. 



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Other SupporMng Tests 

Following are the suppor&ng tests 

1. Spectrum 

2. Refrac&ve index 

3.Magne&c Effect 



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1.Spectrum 



Synthetic spinel colored by cobalt: 

Three broad bands centered at 540, 

580, (Broadest) and 635: 

(Thin Thick Thin) 

Blue Glass colored by cobalt: 

Three broad bands centered at 535, 

590 (Narrowest) and 655. 

(Thick Thin Thick) 

Natural Blue spinel colored by 

cobalt spectrum 

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9/23/12 

2.Refrac&ve Index 

S# Gems RefracMve Index 

(RI) 

1 Natural Blue Spinel 

colored by cobalt 

2 SyntheMc Blue Spinel 


3 Blue Glass colored by 

cobalt 

1.718 Mostly 

1.728 or 1.730 

1.50 or 1.51 or 

1.52 



Mostly. 

comments 

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3.Magne&c Effect 

S# Gems MagneMc effect comments 

1 Natural Blue Spinel 


2 SyntheMc Blue Spinel 


3 Blue Glass colored by 

cobalt 

yes 

None 

Some blue glass 

have weak to 

moderate 

magneMc effect 

and some blue 

glass show no 

magneMc effect . 



I checked many specimen of 

synthe&c spinel of different 

tone but found no magne&c 

effect. 

Note: It is observed that the 

blue glass which show 

yellowish color in SW have 

magne&c property., weak to 

moderate. But blue glass 

show chalky effect in SW 

have no magne&c property. 

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Acknowledgement ,References and suggested reading 

9/23/12 

1.www.MineralsUK.com 

2. hIp://www.minsocam.org/msa/collectors_corner/arc/color.htm 

3. 

hIp://www.gemlab.jkharris.co.uk/Synthe&c%20blue%20Spinel%20and 

%20Co.Glass.html 

4.hIp://gemologyproject.com/wiki/index.php?&tle=Spinel 

Note: 

Everyone can use this presenta&on for educa&onal purpose without my 

permission. Gems & Gemological InsMtute of Pakistan (GGIP)-‐Peshawar 

slogan is “Gemology for everyone”. 

because gemology is not the property of Mineralogist, Geologist, Engineer, IT 

expert, or any other profession or trade which directly or indirectly related to it. 

Hamid Usman KhaIak (HUK)-‐AG Gemologist 



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Gems & Gemological Institute of Pakistan(GGIP ... - Gemology Online

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