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Post by brotherbill on Jan 23, 2024 14:42:18 GMT -5
I have a small parcel of andamooka and need some advice before starting on it.
I have seen lots of examples on the internet of andamooka coated in epoxy. Is this done because the material does not polish very well? If this is the case I would prefer to cap with clear quartz. Conversly if it takes a polish any preferences on the medium used? Cerium, diamond,etc...? Thanks
Last Edit: Jan 26, 2024 5:34:06 GMT -5 by brotherbill
When you use the term "Andamooka" what are you referring to? Amdamooka produced some of Australia's most beautiful opal and still does occasionally. But now the term often means what some miners there refer to as "concrete": an opal-bearing sandstone, usually whitish or tan, that when infused with with sugar and then treated with acid, carbonizes and tuns black allowing the opal's play of color to show.
If that's what you have is it already treated? I've only treated a couple of batches. The blackening is only a fraction of a mm deep and the material is slightly porous. I cut and polished my cabs before treatment for that reason. It seems logical to me that epoxy infusion AFTER the sugar/acid treatment and BEFORE polishing might lead to a harder surface and a much better polish than I achieved. As I recall I polished with cerium.
Post by brotherbill on Jan 23, 2024 17:03:33 GMT -5
gemfeller Excellent answer. You covered everything and more! What I have is black and has an amazing play of color. I was told that it was been treated with sugar and acid. It is porous as you mentioned, probably sandstone as a host. Since the blackness is only surface deep, it makes sense to me to leave the surface as is and cap it with quartz. Thanks for the info.
gemfeller Excellent answer. You covered everything and more! What I have is black and has an amazing play of color. I was told that it was been treated with sugar and acid. It is porous as you mentioned, probably sandstone as a host. Since the blackness is only surface deep, it makes sense to me to leave the surface as is and cap it with quartz. Thanks for the info.
I can't wait to see these. I think I know the material you've got...and if it's what I'm thinking, I expect the capping will accentuate the material quite nicely!
Favorite Quotes: "It always seems impossible until it is done." - Nelson Mandela "Life becomes easier when you learn to accept the apology you never got." - Robert Brault "You can't wait until life isn't hard anymore before you decide to be happy." - Nightbirde (RIP 2/19/22)
Post by hummingbirdstones on Jan 23, 2024 23:33:03 GMT -5
What gemfeller said is correct. It is sandstone matrix. Some is better than others. I have a box of it here somewhere that I deem crap.
Personally I think your idea of capping it is your best bet to get a decent looking cab. Please post a pic when you're done. I haven't seen a nice piece of Andamooka matrix in a while.
Robin
"Of all tyrannies, a tyranny sincerely exercised for the good of its victims may be the most oppressive. It would be better to live under robber barons than under omnipotent moral busybodies. The robber baron's cruelty may sometimes sleep, his cupidity may at some point be satiated; but those who torment us for our own good will torment us without end for they do so with the approval of their own conscience."
FYI there's another type of matrix opal called Fairy Opal. It originates in the Queensland boulder opal fields and is generally similar to the Andamooka matrix from South Australia. It's also a sandstone containing small flecks of precious opal and is treated with sugar/acid and perhaps some sort of epoxy. I've been told it tends to show more red hues than the Andamooka matrix. I've never worked with it but again it's a black opal simulant, not true black opal.
Post by brotherbill on Jan 25, 2024 19:40:14 GMT -5
I ended up going the triplet route. It is nothing to write home about. I didn't manage to get all the air bubbles out of the porous sandstone. I promised pictures...so this is it.
Post by hummingbirdstones on Jan 26, 2024 0:37:29 GMT -5
brotherbill that turned out great! I'm not seeing any air bubbles, just a beauty of a triplet.
Robin
"Of all tyrannies, a tyranny sincerely exercised for the good of its victims may be the most oppressive. It would be better to live under robber barons than under omnipotent moral busybodies. The robber baron's cruelty may sometimes sleep, his cupidity may at some point be satiated; but those who torment us for our own good will torment us without end for they do so with the approval of their own conscience."
Post by brotherbill on Jan 26, 2024 5:40:49 GMT -5
hummingbirdstones There are small air bubbles about pin head size. They are visible under magnification. You know how it is, when you know they are there it is the thing your eye goes to! I will grind the quartz off and try again.
Post by realrockhound on Jan 26, 2024 13:45:03 GMT -5
I hate that. Lil trick that tends to work (maybe you already do this) hitting it lightly with a blowtorch. Generally gets the bubbles to disappear. Sometimes the material has a mind of its own.
Post by hummingbirdstones on Jan 26, 2024 20:42:40 GMT -5
If you feel like you have to redo it, then by all means. If you need magnification to see them, I'd just leave it. It really is pretty as it is.
Robin
"Of all tyrannies, a tyranny sincerely exercised for the good of its victims may be the most oppressive. It would be better to live under robber barons than under omnipotent moral busybodies. The robber baron's cruelty may sometimes sleep, his cupidity may at some point be satiated; but those who torment us for our own good will torment us without end for they do so with the approval of their own conscience."
I think it came out great too! I would be proud to cut a cab like that but I know what you mean about seeing the flaws in your own work. Funny, I watched an episode of "Outback Opal Hunters" late last night and this was the material that one group of them were mining. I had never heard of any opal material referred to as "concrete" and they explained the acid and sugar blackening process.
Last Edit: Jan 27, 2024 11:36:18 GMT -5 by rockbrain
Bigfoot is often called Sasquatch, Yeti doesn't seem to care!
Are the air-bubbles seen in that 1st picture...in the lower left quadrant? I've had that happen on one group of doublets I did...had to scrap them as I couldn't redo the surface agate. Broke my heart! Arghhh...
Favorite Quotes: "It always seems impossible until it is done." - Nelson Mandela "Life becomes easier when you learn to accept the apology you never got." - Robert Brault "You can't wait until life isn't hard anymore before you decide to be happy." - Nightbirde (RIP 2/19/22)
Post by brotherbill on Jan 28, 2024 10:45:27 GMT -5
So I tried twice more to cap the piece with quartz. Each effort turned out worse than the previous. The trapped bubbles look similar to mica. I believe the problem isn't so much getting the bubbles out of the epoxy as it is getting the epoxy to seep down and fill the cavities, remember this stuff is really just porous sandstone with flecks of opal. I like a challenge but know when I am outmatched, for now I will move on!
brotherbill I've been watching this thread and the opal is beautiful. I'm sorry you couldn't get rid of the bubbles. This just popped into my head - have you considered using super glue to seal the opal before adding the epoxy? I'm not sure if they play well together but it may be worth a shot.
Thank you for sharing your experience, I for one appreciate seeing the results, whether successful or not.
Post by brotherbill on Jan 28, 2024 13:24:49 GMT -5
NDK That is an excellent idea! I will try some thin penetrating CA glue. I have some Hot Stuff that gets down in hairline cracks. Might take a couple of applications...but I am back in the game. Thanks.
NDK That is an excellent idea! I will try some thin penetrating CA glue. I have some Hot Stuff that gets down in hairline cracks. Might take a couple of applications...but I am back in the game. Thanks.
That was my original thought. But I'd use HXTAL to treat the porosity instead of the super glue or Epoxy 330. HXTAL penetrates porous material much further than other epoxies. It takes several days to cure and is expensive but the results I've had with valuable materials like gem dino bone seem worth it to me.
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Welcome to the Rock Tumbling Hobby Forum where we share a love of rocks and a sense of community as enduring as the stones we polish.
The RTH Forum of www.RockTumbling.com is an Amazon Associate site and we earn money from
qualifying purchases you make after clicking on our links such as this
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link for instance, or any of our various product ads and banners. By clicking our links every time you begin your Amazon shopping
experience, you are generating a bit of revenue for the forum which helps us cover our expenses. Thank you for your support!
