Those pieces may explain why some of the gold you are finding have gone Johnny Cash.....wear a black coat.
Lol. I wasn't aware that there could be a correlation between these rocks and having gold covered in iron oxides. Guess it makes sense now that you mention it. I've been collecting/polishing chunks of these concretions for years. Have to break them up with a sledge hammer, because they're so damn heavy! Should I be crushing them up instead, looking for gold?
I haven't tried the glass etch you are using Goldwasher. I imagine it's slow but if it's effective that's what matters.
The big boy of cleaning gold specimens is Hydroflouric Acid. This stuff is nasty - as in you die a horrible painful death when you use it incorrectly. If you don't know what you are doing with this stuff and you survive your dangerous acid experiment you will more than likely ruin your first specimen by overdoing the etch. When you over etch you get a lump of melted quartz with a bit of native gold sticking out. That's interesting but not very marketable. This particular acid dissolves quartz and just about everything else, including humans, but it doesn't affect the gold. Finding containers and tools to work with can be challenging since both glass and metal containers dissolve in this acid.
Basically between the environmental dangers of storage and use just having the hydroflouric acid concentrate around constitutes a real hazard. Luckily there is a way to buy and use a very mild hydroflouric acid solution that can get iron stains out in a jiffy and can even do a genuine etch on the rock material given enough time. You are still going to have to wear gloves, have a fresh air supply and be careful when handling the solution but this stuff isn't really any more dangerous than pool acid. No kids, no pets, wear protective gear etc. and you will be fine.
The product is Whink rust stain remover. Whink makes a bunch of different products that might be good for other things but this particular version of Rust Stain Remover is the only one they make that has hydroflouric acid as an ingredient. It's always in a brown bottle but I seem to have a few different sizes.
Whink is not particularly expensive and with reasonable precautions you should be able to use this on your specimens at home. This will dissolve most minerals and metals so other types of specimen might react well too. Rust stains on quartz crystals clean up well and often a dull druzy can be brought to sparkling glory with just a short soak.
Keep in mind that the hydroflouric acid is not your only danger point. The chemical reactions between the minerals present and the acid produce fumes too. Many, if not most, of those fumes are very detrimental to human health and lifespans. You really need to assume whatever mineral you are etching produces poisonous fumes.
Heavy Pans
