Heating of Corundum - an investment?

[minousbijoux]

Michael, lets just say the OP has an unquenchable desire to continue along this vein of baking stones. Would you suggest he/she start with rough instead? Would there be more results - good or bad - to learn from?

 

[chrono]

The dealings with rough will be more difficult. Inclusions can grow in the oven, even causing it to shatter. I'm not even considering the appropriate highly guarded recipes, understanding how to orientate the stone to know if the rough is worth purchasing and more.

As mentioned by seasoned posters and lapidaries, I'm worried many of these stones will show little to no improvement, supposing they survive the heating process as the inclusions expand. Many of these are overly included with one (telltale blue flash) that is suspected of fracture filling. I'm also sure the yellow sapphire with the SLP report is heated and diffused. The overly dark ones probably will not benefit from recutting either because with loss of tone, there is also the corresponding loss of saturation.

As JL is prepared to accept the loss of any and all the stones, at least she is well aware of this losing experiment.

 

[minousbijoux]

Yes, Chrono, its not that I disagree, its just that if JL is serious about undertaking this practice again, it seems to me that the more cost effective way to do it is to use rough, assuming he/she becomes a bit more educated on what to look for in rough.

 

[chrono]

Yes, heating rough is more beneficial than heating cut stones but you'll need a ton of skill and experience to know what to look for, what has potential and what doesn't, the right contacts and more. It's not going to be an overnight or fly by the seat of your pants, learn as you go undertaking, which JL seems to be currently doing. So yes, we are indeed in agreement. I am merely long winded in my explanation.

 

[minousbijoux]

At this point, I was drawing the conclusion, reasonably or unreasonably, that OP has to be doing it more for the learning experience and excitement than because he/she really thinks they can make it work...

 

[JewelryLover]

At this point, I was drawing the conclusion, reasonably or unreasonably, that OP has to be doing it more for the learning experience and excitement than because he/she really thinks they can make it work...

Correct!

 

[chrono]

Then it is an expensive learning experience because many lapidaries and serious collectors have advised against it, knowing well the end result.

 

[JewelryLover]

Then it is an expensive learning experience because many lapidaries and serious collectors have advised against it, knowing well the end result.

It is .. or might be! or wont. I'll see the outcome soon.

 

[Jim Rentfrow]

No matter how many times you are going to shake that 8 ball it is still going to read "lost money" on this deal..........

I admire your willingness to take risks but use the forum to learn from people who have a lot of knowledge and can help you find the areas to make money. A lot of new cutters have done that the last few years and are off to a great start. And a lot of people who didn't listen lost a lot of money very quickly!

 

[Lady_Disdain]

No matter how many times you are going to shake that 8 ball it is still going to read "lost money" on this deal..........

I admire your willingness to take risks but use the forum to learn from people who have a lot of knowledge and can help you find the areas to make money. A lot of new cutters have done that the last few years and are off to a great start. And a lot of people who didn't listen lost a lot of money very quickly!

Yup. As a general guideline, it takes either knowledge, skill, hard work, time or a lot of money to earn money. If something pops up that requires none of these, be very suspicious. What are you bringing to the table for the deal/business proposition/venture? If you can't answer that, the answer is generally "your willingness to hand your money over and get nothing in return." In this case, the key question, as so many others have asked, is "why hasn't anyone else in the supply chain (miner, rough dealer or dealers, cutter, dealer) done the 'obvious' thing and heated these stones?".

 

[PrecisionGem]

Did these stones every come back from being heated?

Curious to see the results.

 

[cm366]

Me too! Even if they came out like these guys, it'll still be interesting....

 

[ChrisA222]

Cm...what the heck???? What the heck am I looking at there? Heating gone bad? lol

 

[chrono]

Are those brown things a protective cast or mould of sorts to better protect the gem and help control the temperature during heating or just some fancy schmancy photographic prop?

 

[innerkitten]

Are they done yet?

 

[cm366]

Heh, neither, that pic was stolen from a blogger who was heating tourmalines a couple of years back. The opaque brown stones were in a batch that got heated too hot for too long (the theory was that one of their kids had twisted the dial, but I don't think they ever found out what happened.) All the stones pictured were from the same lot - the large ones just got BAKED.

 

[chrono]

Goodness gracious! They look fossilized and well.....yes, baked.

 

[minousbijoux]

That is amazing in an awful kind of way. Why didn't the little guys get baked in the same fashion? I'd think the little ones would bake first.

 

[chrono]

Perhaps they were in a different batch?

 

[cm366]

Yep, sorry, didn't make that clear. All the stones were purchased in the same lot, but they were heated separately. I've occasionally had thoughts of heating a few stones for fun - then I glance at this again!

Full disclosure - I have heated zircons borrowing Gene Flanigan's method of candle flame + tweezers. Based on the stones I see him offer, though, he's using nicer rocks and has more experience at it than I do! Still fun to give it a try and watch the colour lighten....

 

[PrecisionGem]

I have found that all the zircons seem to heat a bit different. This could be due to coming from different mine area's. Most of the stones I have worked with are from Tanzania and Nigeria. I have had no luck with Nigerian stones. They will heat to a nice color, but then over the course of a few hours drift right back to an ugly brown.

What I do with the Tanzanian honey brown stones is this. Heat them over the flame, kind of turning them and wiggling them like you would a test tube back in high school chemistry lab. Normally the stones will start going to a deep burnt umber color. This happens pretty quickly, maybe 4 to 6 minutes of heating. Once the go darker, they will quickly start to come lighter. Take them off the heat once this starts. If you heat them until they are the lighter color yellow you are after, you have gone too far, and the stones will continue to turn light and loose too much color. Take them off the heat early, and they will continue to turn. Once they cool they will look fantastic. Now, over the course of a day or so, they may or may not drift back toward the honey brown color. If this happens, repeat the heating. There is almost always some drifting back.

They all heat differently, but it's lots of fun.

I would think that if you are dealing with a stone that you bought cut, it most likely has been heated to it's best color, so you may not have too much luck.

 

[minousbijoux]

Now this is a first. Other than the rudimentary kunzite in chicken recipe we got from Pandora and LD a while ago, this is the first time we've received a real recipe on how to cook stones, complete with "wiggle" motions, and a test for doneness! This is like America's Test Kitchen for gemstones! Thanks, Gene.

 

[ChrisA222]

Too bad it only works to turn honey-browns into yellow.

I want to turn my yellow ones blue! Or, my red ones into hot pink or something lol

 

[JewelFreak]

Hmmm, I was just thinking about cooking for Thanksgiving when I saw that photo. Guess that won't be on the menu.

Thanks for the Julia Child method for zircons, Gene. Good point, though, about cut ones.

--- Laurie

 

[innerkitten]

That's a charred tourmaline!?

 

[PrecisionGem]

Too bad it only works to turn honey-browns into yellow.

I want to turn my yellow ones blue! Or, my red ones into hot pink or something lol

Chris, you can heat the red ones the same way, and they will usually lighten. I have found that the red stones generally take longer to heat as they need a higher temperature. Sometimes I'll heat the red stones in my oven. The temperature I use for them is 842 deg F. The yellow stones, if I cook them in the oven are usually around 675 F. It's best to start at lower temperatures, as you can always re-heat. Pretty much any zircon can be cooked to be colorless if you go too high. I have taken some of the ugly brown stones from Nigeria, and cooked them colorless. To do this you might need to get up over 900 F.

 

[PrecisionGem]

Here's a before and after heating of a Tanzanian Zircon. This one was most likely done over an alcohol lamp.

 

[chrono]

The Art of Cooking Gems over the summer BBQ flames.

 

[Karl_K]

Here's a before and after heating of a Tanzanian Zircon. This one was most likely done over an alcohol lamp.

I like the before color much better!

 

[PrecisionGem]

Here's a before and after heating of a Tanzanian Zircon. This one was most likely done over an alcohol lamp.

I like the before color much better!

The before color never sells.