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Techniques for CollectorsCleaning iron stain on Prenite

20th Jan 2014 17:38 UTCDanny Jones Expert

Can anyone tell me if Iron Out will damage Prenite that has a small discoloration of iron on it?

20th Jan 2014 18:13 UTCSteve Hardinger 🌟 Expert

Prehnite can withstand extended treatment with Super Iron Out.

20th Jan 2014 20:53 UTCGary Moldovany

I have cleaned quite a few prehnite specimens with Super Iron Out. It's hit-or-miss. Sometimes they come out looking great and sometimes they look like a piece of junk. Don't make the solution too strong and don't leave the specimens in solution for any longer than is necessary. If they come out with a dull finish, you may be able to restore the shine with a light mineral oil treatment. Good Luck and please post some photos! Gary

20th Jan 2014 21:07 UTCRock Currier Expert

Where is the prehnite specimen you wish to clean from?

20th Jan 2014 22:15 UTCDanny Jones Expert

Rock the prenite are from Morroco

23rd Jan 2014 21:42 UTCRock Currier Expert

Danny,

Most of the prehnites from Morocco are rather weathered looking and I suspect that they are dug from near the surface. I do't think that any use of iron out in any concentration will hurt them. If the "iron stain" in actually included in the prehnite, then the iron out won't do any good.

26th Jan 2014 17:44 UTCMark Heintzelman 🌟 Expert

Rock,

I've been wondering about this myself. Since you've chimed in on this, do you mind if I might ask for your opinion on whether this Coopersberg Prehnite would benefit/survive a treatment in super-iron out? Obviously it had some secondary micro pyrite which altered in-situ, causing some staining. My main concern is the delicate nature of the cockscomb xtls, as opposed to the compact radial aggregate from the NJ traprock.

I'm sure you know that specimens in any quality from this find are as rare as hens teeth, so I don't want to put this in one at risk unnecessarily. I've been "on the fence" about this one, and could use an opinion from someone who has some experience with chemically treating a larger variety of specimens, from here AND there (and over there too). :D

MRH

26th Jan 2014 19:16 UTCRock Currier Expert

Mark,

That's a rare specimen indeed. I have had only one and that one I bought off of Wards when they got in a big old collection for sale that included some full hand size single azurite crystals from Tsumeb. Charlie Key was competing with me for first pick and snagged the azurites. I also got a wonderful thomsonite from the Wachungs in that deal. I eventually gave the prehnite to Arthur Montgomery since he had given me some fine small things for my collection and had written the Minerals of Pennsylvania book.

What are the black/brown specks on the specimen? Have you tried just "blasting" them off with a fabric gun? I would not worry about putting it in Iron out at all, but you might try picking a bit of the black/brown stuff off with a needle and and a bit of the prehnite and putting it in a test tube and watching what happens. Examine them well with a microscope before you put them in and then again after a few hours.

27th Jan 2014 16:31 UTCMark Heintzelman 🌟 Expert

Rock,

They appear to have been micro pyrite, altered to limonite in-situ. I had intended to physically remove whatever remnants of them I could (with a probe under the microscope) prior to any treatment. Sound advice, I will see if I can remove a small sample of the prehnite, to test how the solution might effect it's luster. Thanks for the encouragement.

MRH

27th Jan 2014 16:39 UTCRock Currier Expert

Its probably altered pyrite. You might wish to considering using an air abrasive tool. Prehnite is pretty tough stuff.

2nd Feb 2014 17:15 UTCMark Heintzelman 🌟 Expert

Well, here are the results.

Overall I'm pretty pleased. The luster was not affected by treatment on the test chips, and since this piece is solid prehnite, there were no additional concerns to address. I removed most of the remnant altered pyrite prior to treatment, but some of it still remains as they had developed wedged between the blades and were simply inaccessible.

All in all, it looks much better, my sincere thanks for the info and encouragement! The pale and translucent nature of the Prehnite and the erratic positioning of the xtls in this piece excludes this as a "display" specimen (shows no contrast, the xtls nearly "disappear" even when viewing it at a relatively close range), but it now looks less like something just picked up off the pile. Hopefully if someday it finds it's way into unknowing hands, it will at least be better appreciated, and thus better treated, than it might be with the way it looked before.

MRH

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