Heat treating Cambodian zircon

Just about to attempt heat treatment of Ratanakiri Cambodian brown/coke cola zircon.

Anyone experienced this process.

I have an electric kiln and purchased some graphite crucibles for the exercise.

Aim is for a traditional brilliant sky blue.

Not the answer you're looking for but I thought it shows what you want to do.

[video=480,360]https://youtu.be/AzIshb6UZ9E[/video]

This may help though.

https://www.prospectingaustralia.com/forum/doc/member-docs/3008/1546171043_effect_of_heat_treatment_on_color_of_natural_zircon..pdf

Why do you want to ruin a good stone by heat treating.... Heat treatment and 'Fakes' are killing the Industry... Or a better way to put it is 'they' are making a killing out of it...

LW....

Oh dear. May i suggest you research Ratanakiri Blue Zircon.
Far from ruining a natural stone, very special heat treatment creates stones like no other and are found only in this area.
This is not a case of colour lightening of dark stones, it is a unique gemstone.

Pretty Stone But..... All good, If that's what you want to do, Go for it...
and show us some pics of the finished product. ..


LW...

LoneWolf said:

Why do you want to ruin a good stone by heat treating.... Heat treatment and 'Fakes' are killing the Industry... Or a better way to put it is 'they' are making a killing out of it...

LW....

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It's not the heat treatment and fakes that's killing the industry, it's the non-disclosure that needs to be stamped out.

I've got nothing against heat treating a stone for colour enhancement provided said stone is for your own collection, but when it is offered for sale without disclosure, that's a different thing altogether.

As for offering fakes, I've got nothing against re-introducing public floggings as a weekly spectacle.

Jeff

Good luck Pete - what temperature and time are you thinking of ? Looks like there is a big difference in the result for sealed or unsealed crucibles.

I have always wondered what Australian zircons would do under heat treatment.

Would love to see some before and after photos.

Wally,
I packed it into a graphite crucible with crushed heat beads and heated for two hours at around 900C in an electric furnace. The aim - to generate a reducing atmosphere.
The stone went in as shown and came out white diamond clear. Apparently some do that rather than turn blue.



It has amazing second order colours in bright light and although the photo is poor, it is a really bright and impressive stone.

Pete's Pick said:

I packed it into a graphite crucible with crushed heat beads and heated for two hours at around 900C in an electric furnace. The aim - to generate a reducing atmosphere.
The stone went in as shown and came out white diamond clear. Apparently some do that rather than turn blue.

Click to expand...

Interesting. Where did that cooking info come from?

I ask because the university that studied cooking those stones to get the best blue from those stones used a somewhat different method. Hotter and a lot longer for best results.

Also heat beads contain an oxidizer :argh: (probably Sodium Nitrate) which probably didn't have any affect but maybe worth avoiding next time since you are trying to achieve a reducing atmosphere.

Heat Beads said:

An oxidising agent is used to make the briquettes easier to light. This material is a salt, often used as a food preservative. Without it, the briquettes would take a long time to light and require more firelighters.

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Correct. Just that i got really impatient and couldn't wait so used what was at hand.

I will try more and yes, i suspect i read the same research suggesting 1400 deg C.

But i also read others suggesting 900 for two hours. And my furnace won't go to 1400 so i concocted a recipe. I am not unhappy at all. I was hoping for blue but this was a lot of fun and a lovely result.
The lustre is amazing. Started out greasy. But cut, exhibits real "fire" and brilliance, which gives it a shiny, freshly polished look. And it is very slippery in the hands, unlike any quartz, citrine or sapphire i have cut.

Pete's Pick said:

Correct. Just that i got really impatient and couldn't wait so used what was at hand.

Click to expand...

Sounds like something I'd do - get impatient and improvise, for better or for worse.

That paper recommends graphite. I wonder how pure door lock graphite from the hardware is? Just a thought.

Anyway look forward to seeing and hearing about your results. Something I'd enjoy doing, a type of alchemy, but barely have the time to cut. Never mind sourcing decent rough and spending time experimenting with cooking.

Good luck with the next lot. :Y:

Thanks Pete, nice shaped rough. I love how a finished zircon plays with the light. :inlove: bloody hard to photograph though :awful:

I found the university study very interesting, looks like they got a lot of clears at lower temperatures with sealed and unsealed crucibles. Thinking I would try 1100deg and a simple covered crucible for about 2 hours, it seemed to me to be their sweet spot........funny how we all conclude our own ideas. :lol: :lol: