oxalic acid

[stdenis_jd]

Some of you may already know this, might actually be common knowledge, but oxalic acid is absolutely amazing for removing iron/tannin/oxidation from rocks.

I collect all kinds of rocks like the rest of you but have a special liking for drummond island pudding stones (Google images or Wikipedia for pics). Just love the look of em for polishing, landscaping, etc. They are basically a coarse grained sandstone matrix (usually off white which is good qualiy to brown which is usually undesirable) with chunks of brightly contrasting rocks conglomerated in them, mainly red/black/pink and banded Jasper, some hematite and some other various ones.

There is quite a lot of iron in the ground here in Michigan, and in the rivers a lot of tannin so these rocks get stained pretty bad, taking a great stone and making it look like it's been soaking in sewage. Usually I am able to use a coarse wire brush and clean the algae, most of the tannin and other such blemishes with a little elbow grease, but some of them are so porous and badly stained that it doesn't work (plus these rocks are mostly quartz so the metal does nothing to the rock, but the brushes get ruined pretty easy lol). I tried out TSP (trisodium phosphate) and it did absolutely nothing after soaking for about 48hrs. 24 hours in with wood bleach (Thompson's water seal) and it ate off nearly all the oxidation off the smaller palm-sized stones and it is making some serious progress on a 25# stone with very deep and dark staining. I think it will take the better part of a week, but pretty sure it will eat it away :-D

Just thought I'd share that with those of u that don't know and have some otherwise nice looking rocks that look like hammered turds from the iron staining and such.

 

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[kingskid1611]

I would have assumed those were botched cement stones someone tried to make.....lol Interesting

 

[stdenis_jd]

I would have assumed those were botched cement stones someone tried to make.....lol Interesting

Haha funny you say that because when ppl see them in general that's what they think :-P
Here's a couple pics of some new additions

 

[stdenis_jd]

In that bottom pic, you can see the one in the background that has pretty bad iron staining. That one looks almost as good as the one on the left now :-)

 

[meMiner]

I like playing with oxalic acid (outside) to clean rocks too. I usually try something mild like coke or vinegar, then CLR the oxalic. I also try muriatic on the right stuff (usually to dissolve calcite off native silver). I like the look of a partial cleaning, leaving some of the rock attached.

 

[stdenis_jd]

Before:


After:


The "Before" pics are after getting them out of the river and scrubbing for about 20minutes with a hard bristled steel brush. The "after" pics are after soaking for about 48 hours in wood cleaner (with ~10% oxalic acid content) then a light water rinse and brush cleaning.

 

[stdenis_jd]

Going to Drummond Island, MI this upcoming weekend the virtual epicenter of where these conglomerates were created...I'll bring back some nice pics I'm sure (as well as some sweet additions to my collection Haha)

 

[MrLee]

Yes, Oxalic is the entry to the cleaning/etching world. John Betts Fine Minerals has a nice description on cleaning acids. Many iron out, rust off is easily obtainable at most hardware stores. I'm using some to clean Amazonite specimens right now. A little slower than the muratic acid I'm use to, but safer!