Paleoworld-101 Posted March 29, 2011 Share Posted March 29, 2011 I recently went with my family up to Lighting Ridge in NSW (a well known opal and opal fossil source). While i was there, i went fossicking for about 5 hours and managed to find lots of potch pieces (non colourful worthless opal). But, i did find one piece of real Opal (full of dazzling colours). I know it's not a fossil, but how would i extract it from the matrix without damaging the actual opal (it's surrounded by sandstone/claystone). I read lemon juice or vinegar might work, but it has no effect on the rock. Do i need a stronger acid like Hydrochloric? "In Africa, one can't help becoming caught up in the spine-chilling excitement of the hunt. Perhaps, it has something to do with a memory of a time gone by, when we were the prey, and our nights were filled with darkness..." -Eternal Enemies: Lions And Hyenas Link to comment Share on other sites More sharing options...
bear-dog Posted March 29, 2011 Share Posted March 29, 2011 Try a chisel and hammer ,chisiling away from the piece.Acids have harmful vapors that can also drift over and harm the opal.Be careful though as opal fractures easy. Bear-dog. Link to comment Share on other sites More sharing options...
Frank Menser Posted March 29, 2011 Share Posted March 29, 2011 Not an expert on Opal, but remember that Opal is basically Silicon dioxide - with water. It is that part of its makeup that concerns me when it comes to using any kind of chemical on it; as the opal might absorb it and possibly be ruined. Acid is used on rock that has a high quantity of calcium carbonate which disolves easily. Likey your rock doesn't have much of it. Also, Opal is fairly soft .55 moh as I recall. So careful when using mechanical means. It has allways been a dream of mine to visit the Cooper Pedy mines. There should be someone there who can advise you on the safest way to extract the Opal from its matrix. Be true to the reality you create. Link to comment Share on other sites More sharing options...
BobWill Posted March 29, 2011 Share Posted March 29, 2011 Welcome to the forum. You can use acid on limestone. For sandstone and clay just careful abrasion. Link to comment Share on other sites More sharing options...
Willow Posted April 15, 2011 Share Posted April 15, 2011 Hi there, I will be doing an opal cutting and polishing course here soon (starts 26th of April). What I can already tell you is that the sandstone is normally removed by abrasion using grinding and sanding equipment. Depending on the size and colours within your stone, it could be quite valuable and it is very easy to either crack it or simply lose value by incorrect cutting or polishing. If I were in your place I would visit one of the reputable opal sellers in sydney and see if they can polish the stone for you or wait until you next visit here to have it done. Even people skilled in opal cutting do have failures from time to time, simply because opals are so fragile and may have flaws, for that reason I would not take the stone to your local jeweller to have it cut/polished. Hope this helps, after you have it done I would love to see a pic. Willow Link to comment Share on other sites More sharing options...
Willow Posted April 15, 2011 Share Posted April 15, 2011 Back again, Opal is 5-6 on moh. Link to comment Share on other sites More sharing options...
ragegamr Posted February 16, 2017 Share Posted February 16, 2017 I recently went to cooper pedy and returned with some opal chunks (worthless, just wanna get rid of the rock to make it look nice). I tried using a chisel but I ended up making more of a mess. Obviously not too worried as the chunks aren't worth anything anyways. Link to comment Share on other sites More sharing options...
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