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 Post subject: Large Chrysoprase
PostPosted: Thu Jun 25, 2015 12:11 am 
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Hi All
We have found a very large chunk of vein hosted chrysoprase (in a dry creek bed) - we haven't got it cleaned up yet. Its about 40kg with perhaps 5% external weathered Gabbro and about 50cm * 40cm * 25cm. Don't know what to do with it at all from here. Not even sure how to go about cleaning up something that large. Anyone have any ideas how to best go about it?


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 Post subject: Re: Large Chrysoprase
PostPosted: Thu Jun 25, 2015 12:21 am 
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Hello and welcome.
I've moved this post to a more appropriate area.


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 Post subject: Re: Large Chrysoprase
PostPosted: Thu Jun 25, 2015 7:54 pm 
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Really cool! Can you give an approximate location? Australia perhaps?


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 Post subject: Re: Large Chrysoprase
PostPosted: Thu Jun 25, 2015 8:31 pm 
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dchallener wrote:
Really cool! Can you give an approximate location? Australia perhaps?

Hi
Yes it was Marlborough in Queensland. I don't know how to upload images here, but its fairly milky on the edges, but you can see little windows through the host rock into the center and its a lovely green. With a specimen this large it could obviously be used for some large sculptures, so as much as i want to take the saw to it and have a look inside, we are not going to do that!

Anyone advise the best way to clean it up, is it best to chip the outer rock layers off carefully with a chisel, what about soaking in HCl? any advice would be warmly appreciated.


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 Post subject: Re: Large Chrysoprase
PostPosted: Thu Jun 25, 2015 11:15 pm 
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Pics?


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 Post subject: Re: Large Chrysoprase
PostPosted: Fri Jun 26, 2015 1:37 am 
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I just added the pics as an attachment, i looked at the 'how to post a picture on the forum' link and a saw the word 'coding' somewhere and immediately had to have a drink and a lie down. :)

the pics are pretty ordinary, they don't do the green colour a lot of justice, but there you go. i'll have to bring my camera into work to take some good macro shots in better light. I think the photos show that there is just a thin veneer (up to about 15mm) of quite weathered host rock, but for the most part this is just staining.


Attachments:
photo 2_600.JPG
photo 2_600.JPG [ 157.01 KiB | Viewed 1100 times ]
photo 1_600.JPG
photo 1_600.JPG [ 121.56 KiB | Viewed 1100 times ]
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 Post subject: Re: Large Chrysoprase
PostPosted: Fri Jun 26, 2015 8:06 pm 
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NB5225 wrote:
Anyone advise the best way to clean it up, is it best to chip the outer rock layers off carefully with a chisel, what about soaking in HCl?


I doubt if soaking in HCL would do anything positive. Better might be to use one of those wet sandblasters that you hook up to a pressure washer. Using coarse AlO2 grit and some time might get you a clean and smooth surface, but probably not deep enough to see into the stone very far.

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 Post subject: Re: Large Chrysoprase
PostPosted: Sat Jun 27, 2015 8:56 pm 
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Wow NB5225, that's an enormous piece of citron chrysoprase. The value in that stone obviously lies in its size. Sure, it would sell quicker cut into pieces but cutting costs, posting etc would limit the potential for profit.
As Michael indicated, sandblasting it would enable a prospective buyer to evaluate the rough better, which if its a quality piece could really add to the selling price. However, if your going to loan it to a local museum leave it as is.
Finding the right buyer willing to pay close to its real value will be difficult and as much as I'd like to say transform it into a sculpture, it would cost a lot, be difficult to achieve a quality result (due to its hardness) and only appeal to select buyers.
I think your best way to sell it is to contact a local chysoprase mine and see if they are interested in selling the piece on consignment. They have access to serious buyers. Just make sure you don't get scammed in the process of selling whichever way you go with.
I'm no expert and I may be well off here, but I'd be asking around the AUD$10k mark if the quality is good all the way through. I know premium nickel green chrysophase rough gets up to AUD$1 per gram so imo AUD$0.25 per gram ($250/kg) for your piece might be reasonable. Best of luck.

Cheers,
GR


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 Post subject: Re: Large Chrysoprase
PostPosted: Sun Jun 28, 2015 7:48 pm 
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Thanks GR

It is difficult to tell the internal quality, it is well faded on the outer surface and is a citron colour, and well eroded/pitted, but from where the quartz is exposed through the underside there is a nice translucency and a good emerald colour. Obviously because of its size the only way to tell is dissection, but i'm reasonably confident the internals are a much nicer green than the outside. Thanks for the advice. Wet sandblasting seems to make sense, and we have a good supply of a topaz sand for abrasives, we'll do that this weekend. We are planning on heading back up in the next few weeks to the same spot we found this bit. No amount of Queensland flooding could move this piece very far at all as its so heavy, so i'm hopeful there is more of this vein in the same spot.

Thanks again


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