[Rockhounds] Re: Heat treating agate to get carnelian

[Carol Carter-Wientjes]

Rock,

Thank you so much for all of that info, very interesting stuff going on "out 
there". I know that black onyx is a product of the sulfuric acid 
carbonization treatment and is a long process. Incorporating nails to 
produce a specific tone of green was pretty ingenious of your friend.

As for the agate that prompted me to ask about heat treating, it's a type of 
carnelian from Hemlock Lake in Oregon. 2-3 mm of the surface is a beautiful 
orange-red but any deeper inside, the material is mostly clear with a hint 
of orange & some isolated spots are dark orange. I cut off a couple of slabs 
which I suspect will darken with some heat given the tint that's already 
present, am hoping so anyway.

Fri a.m......that's as far as I got with this email last night, then saw Jim 
Small's post this morning that said:

"For instance, much Oregon carnelian comes from the ground with a reddish 
skin, and is much paler inside; heat-treating improves the body color to a 
close match, especially after slabbing."

Excellent! Thanks, you couldn't have picked out a better example Jim! I'll 
be roasting the slabs sometime next week and will let you guys know what 
happens.

TGIF and Have a Gneiss Weekend, Carol


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