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Techniques for CollectorsCleaning St. Clair, Pa. fern fossils

9th May 2018 21:13 UTCEd Clopton 🌟 Expert

Does anyone have experience with chemical cleaning of St. Clair, Pennsylvania plant fossils? The rock is a black slate, and the fossil impressions are lined with white pyrophyllite that makes for striking specimens. I have a nice large one that is stained with iron oxides. Can the iron oxide be removed, or at least lightened up, by soaking in Iron Out or some other rust remover? Scrubbing would do more harm that good, but it seems like the pyrophyllite should not be affected by the chemicals.

10th May 2018 15:39 UTCDonald B Peck Expert

Hi Ed,

I agree. I don't think that SI will hurt the pyrophyllite, but I would try a piece i didn't care about before the ggod ones.

Don

10th May 2018 20:51 UTCMark Heintzelman 🌟 Expert

These also represent the only Pyrophyllite occurrence in all of Pennsylvania, so a "must have" for us PA collectors.

Actually, I'm not aware that anyone regularly, or has even attempted to treat these with Iron Out. The real trick is to encounter a seam that hasn't been unduly stained by iron from the unstable pyrite these measures are well known for. You are right, in that these have to be treated with care. The majority of the pyrophyllite can be scrubbed off readily, and all that will remain is the fossil impression in the slate. My display piece, as you can see, has some yellowish iron staining, but I consider it acceptable for the size and coverage. I have a few smaller ones which are pure pristine white (for Pyrophyllite reference material). Here is a microscopic view of the fibrous,layered nature of this material. I have my doubts that any noticeable improvement might be had, but it's certainly worth a try. Look forward to hearing back about it . . Good Luck!

Pyrophyllite replacing Alethopteris (seed fern) Llewellyn Formation (St. Clair, Schuylkill Co., PA) 10'' x 6" + micro

10th May 2018 21:46 UTCJeff Weissman Expert

Pyrophyllite and reference added to the locality page (https://www.mindat.org/loc-28811.html), you can post your images now, Mark! Now, time for me to get a sample.

11th May 2018 00:30 UTCMark Heintzelman 🌟 Expert

Thanks Jeff.

I also have a fairly sizable cubic Pyrite on matrix sample for this region that I acquired from Ron Slotto some years back. It's of course sitting in the "disease ward", so I really should get a better image of it and post it here before it's too late.

MRH

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