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Cleaning Gold Specimens - Step By Step Methods


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If you are wanting to clean your specimens and turn the quartz snow white then the only acid or cleaner you need is muriatic acid. Period. If you want to clean the gold and lightly clean iron deposits off the specimen then something else that is less agressive.  Maybe nitric acid or wink. If you want the manganese staining to go way, muriatic is the way to go. To neutralize the muriatic acid thoroughly, you need to soak it triple the time with baking soda water, that you had it in the acid. You can soak it in muriatic longer to turn quartz snow white or less time if you want some of the coloring in the quartz to stay such as rose coloring or yellowing from alteration.

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If you want to strip the quartz from gold completely, then hydrofluoric acid will do the trick, but this stuff is far beyond just dangerous, it is deadly. You absolutely have to neutralize it in a strong solution of baking soda water for triple the time in acid and at least two or three times with in the triple time period you should pour out the soda water and pour in a fresh solution of soda water. Hydrofluoric will pass rapidly through your skin and go to your blood stream and continually wreck havock on all your internal organs and eventually kill you. I had a very close call with this stuff dripping down a chemical glove and came about  a half inch to an inch from dripping onto my forearm. At that point I said never again will I mess with hydrofluoric acid again. If you get it on your skin even a small drop, spraying it with soda water is not going to help you. A better alternative to it is hydro-shocking the specimen. I wrote an article on this in the icmj mining journal and it is also in my book.

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Technically a strong base should dissolve quartz just like a specific acid like HF. Not saying anyone should try this, but scientifically speaking there is no reason why lye (sodium hydroxide) or maybe even potash heated up to a liquid wouldn't dissolve quartz too since they will rapidly dissolve glass when heated. There may be a chance it'd react with the silver/copper in the gold alloy though?

Maybe a good reason no one ever talks about speci prep with bases, or maybe not. Glenn, you or anyone else ever tried this?

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2 hours ago, Gerry in Idaho said:

Glad you know what you are doing.  I was already quite impressed with specimen B before the cleaning, but am excited to see how much better it looks afterwards.

Unfortunately using the weaker acids it sometimes can take a long period of time to achieve good results. I've had good results in a couple days to several months. Hopefully the specimens I selected won't be in the several months category.

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31 minutes ago, jasong said:

Technically a strong base should dissolve quartz just like a specific acid like HF. Not saying anyone should try this, but scientifically speaking there is no reason why lye (sodium hydroxide) or maybe even potash heated up to a liquid wouldn't dissolve quartz too since they will rapidly dissolve glass when heated. There may be a chance it'd react with the silver/copper in the gold alloy though?

Maybe a good reason no one ever talks about speci prep with bases, or maybe not. Glenn, you or anyone else ever tried this?

Hey jasong,

Fortunately most of the type of gold specimens I find are in shale or shale with limonite. Some other small quantities of minerals get mixed in specimen and can complicate the cleaning process.

You have a interesting concept of using a strong base. I'm no geologist or chemist and would have to run by someone with the knowledge of the chemicals being used on specific mineral specimens. I know using the weaker acids and heating them improves the cleaning process.

Hopefully someone else will chime in.

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Yep for sure, I get my CLR up to boiling and it speeds up the caliche removal on nuggets by like 10x. I'll dump hydrochloric into a black bucket and let it sit in the sun for various rock/gem specimens too.

Hmm well since I can't find any record of anyone trying boiling lye, I might give it a try this summer when I can do it outside. I'm curious if it leaves a different look/finish to the quartz than HF does? And just to be clear, I'm not recommending this to any of the general public reading this thread. Safety issues just as bad as HF, or worse than diluted stuff like Whink. :smile:

Looking forward to your next installment of photos. Seeing specimens exposed reminds me of going into older houses and stripping away 100 years of wallpaper and linoleum and exposing the original beauty, it's a fun process to watch.

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Beware of boiling  hydrochloric in a non vented area. You will get a lot of fumes that are dangerous and corrosive. Don't ask how I know!

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Geof, sounds like a good story for all to hear. Better to learn from others mistakes when dealing with the topic we all are talking about. Words of wisdom, you know. You have a good point with that comment. When I first started to use muriatic acid years ago, it was for the purpose of identifying carbonate rocks. I kept the jug in a side compartment in the back of a Subaru I used to have and in the compartment I had other items, knit gloves, a topo map of a good area for gold which was doctored up with likely spots by the chief mining engineer from the Montana bureau of mines, and a larger forest service map. A few weeks after I put it in there I opened up the compartment to get the map and I saw the maps were missing sections. It looked like a mouse got to it. I picked them up and they just crumbled into tiny pieces. The gloves also became brittle. Don't store it near anything you don't want destroyed by the fumes venting off of it, even if the cap is on and secure. It will still affect it.

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Someone described nitric acid as less aggressive than muriatic acid (HCl).  I would never use nitric acid except under professional supervision in a hood. I have use HCl at home since high school.  I carried it around in my pocket.  While its vapors will corrode nearby metals etc., it is not a powerful oxidizer like nitric acid which I regard as extremely dangerous.  Perhaps the commentator was referring to its action on minerals as being less aggressive not to safety issues.  I think it is best to avoid any misunderstanding by mentioning nitric acid is a dangerous material.

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PART FOUR:

This picture was on the previous post which shows the gold specimens reaction to Whink for the first time:

1885175212_100_3595a(2144x1608).thumb.jpg.882abfbf10f95af8330a3adac8c45602.jpg

The following pictures show the reaction to Whink after a week of soaking:

1527056022_100_3596r(2381x2302).thumb.jpg.903bddec0f3ee59804dea1ffac5d14e0.jpg

914988812_100_3609r(2481x2273).thumb.jpg.7dbd28f094d371eed287a8ee0a7b298b.jpg

1556945484_100_3606r(2866x2234).thumb.jpg.51557a396ab1f20e24df921d472620a5.jpg

As you can see there is some reaction to the gold specimens using Whink during that time period, more reaction on some than others. The following picture are the gold specimens taken out of the Whink solution and placed in gold pan for a closer view. Specimen B did not stay intact as I hoped, but that's the way it goes sometime and it shows great progress on the larger piece and smaller piece is almost cleaned. Specimen A doesn't show a lot of progress at this time. Specimen D does show some progress and Specimen C is almost ready for the next stage. All of the gold specimens are placed back into a fresh batch of Whink solution for another soaking.

1541399133_100_3616r(2698x2307).thumb.jpg.741b3b96e70cb96efe75af361fe906c7.jpg

During the time period in which the gold specimens were soaking there will be some loss of gold to some of the specimens, especially the wire gold specimens. The following shows some of that loss:

1247007905_100_3621r(2144x1608).thumb.jpg.81b2aec14285765492df1d05ef7117b2.jpg

Part Five I will discuss the next stage of the cleaning process and where I will use a little more aggressive cleaning technique and achieve better results.

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