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 Post subject: identifying black spinel and onyx
PostPosted: Sat Dec 01, 2007 10:21 pm 
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Hi,

I am new to this but I need to be able to identify genuine black spinel as opposed to black onyx. I realise spinel is harder but is there a way to tell them apart easily? Is there some simple test equipment I could buy?

I should mention that I am trying to make the identification of stones that are already set in silver jewellery. I live in THailand which apparently is one of the few sources of black spinel having a mine in Kanchanaburi but even local traders there refer to black spinel as being black onyx - hence my confusion.

Thanks for any help


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 Post subject:
PostPosted: Sat Dec 01, 2007 11:17 pm 
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Posts: 1795
Location: canada
hi john101:

If you don't have trhe equipment to separate the two you cab buy guaranteed blck spinel from

http://aussiesapphire.com.au/

direct from the mine. :)

the numbers for black spinel are:

RI: 1.718
Singularly refractive
Specific gravity: 3.5-3.6 ...
CLEAVAGE None
HEAT SENSITIVE No

WEARABILITY* Excellent


the numbers for black onyx are

REFRACTIVE INDEX 1.544 - 1.553
HARDNESS 7
SPECIFIC GRAVITY 2.651
CLEAVAGE None
HEAT SENSITIVE No


hope this helps

_________________
A Chinese proverb says "Gold is valuable, Jade is Priceless."


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 Post subject:
PostPosted: Sun Dec 02, 2007 9:07 pm 
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Posts: 189
Hi

The faceted black spinel which I saw a lot of in Thailand and which was all referred to as "black onyx," had a noticeable higher luster and sharper faceted edges - they both are listed as having vitreous luster in texts, but side by side, I see a luster difference. If you buy some specimen stones for comparison I think you will see the difference - especially with a loupe and a good light.... look at the fracture surfaces (spinel is chonchoidal and vitreous) and see if light behind the stone shows any banding near the thin edges. A refractometer reading would be your best proof, though not always possible of course - the black spinel will have a higher RI than other spinel - 1.740 up to 1.777, much higher than chalcedony (black onyx).


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 Post subject:
PostPosted: Sun Dec 02, 2007 10:17 pm 
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Posts: 5
I do have some supplier contacts in Kanchanaburi for loose nin stones as well as silver jewelry with nin but if you think you can be competitive on price then please get in contact; jae@loxinfo.co.th

ines and 9
wolf wrote:
hi john101:

If you don't have trhe equipment to separate the two you cab buy guaranteed blck spinel from

http://aussiesapphire.com.au/

direct from the mine. :)

the numbers for black spinel are:

RI: 1.718
Singularly refractive
Specific gravity: 3.5-3.6 ...
CLEAVAGE None
HEAT SENSITIVE No

WEARABILITY* Excellent


the numbers for black onyx are

REFRACTIVE INDEX 1.544 - 1.553
HARDNESS 7
SPECIFIC GRAVITY 2.651
CLEAVAGE None
HEAT SENSITIVE No


hope this helps


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 Post subject:
PostPosted: Sun Dec 02, 2007 10:45 pm 
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Posts: 1795
Location: canada
Hi John101:

http://aussiesapphire.com.au/ does not belong to me you would have to contact andrew yourself> to work out a deal.
:)

_________________
A Chinese proverb says "Gold is valuable, Jade is Priceless."


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