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Techniques for CollectorsHow to Clean This Goethie Pseudo. Cluster of Tenacious Clay?

13th Sep 2018 00:56 UTCSteven Renaud

I went to the "hilltop clay pit" in Utah to collect goethite pseudomorphs. While most of the clay deposited on my goethite specimens came off with a simple bath and nylon brush, my largest specimen is proving difficult to clean.

The clay is super hard, maybe it's now 'mudstone'? I am no geologist, but this deposit only comes off in chips by a brass pick and barely by vigorous brushing with brass.

One idea that I haven't been able to try is immersing in an extended heated bath, might that loosen the clay? If you have another recommendation, I'd love to hear it. I'd be really sad to see my best find of the trip with this as it's final state.

Here are photos uploaded to an external image hosting site: https://imgur.com/a/tiCCO2w

Thanks!

-Steven

13th Sep 2018 19:44 UTCDoug Daniels

A late fossil dealer/friend would sometimes use a potassium hydroxide solution (NOT sodium hydroxide, common lye) to loosen clay coatings on fossils specimens. Don't know for sure how well it worked, and it may depend on which clay mineral was coating things. Another chemical used for clay dispersal (well, in sediment samples) is sodium hexametaphosphate; may or may not work, I've never used it on solid samples. The problem with either chemical is getting them, and at first in a small quantity to see if they would work. Of course, if you can obtain one or both, be sure to test an insignificant piece first, and not the one you really hope to clean up.

13th Sep 2018 22:33 UTCWayne Corwin

I would think a "Mystic Pressure washing gun" would make easy work of it.

14th Sep 2018 02:07 UTCSteven Renaud

Thanks Doug, I'll try the potassium hydroxide if my extended hot water bath doesn't work. Seems I can buy KOH online, though there's a hazardous material surcharge for delivery. I'm sure that's not cheap. You can buy KOH flakes meant for soap making at Lowe's, apparently.

Wayne, I neglected to mention this but alas, the last layer of clay(?) is not effected by my spot cleaning gun.

14th Sep 2018 03:28 UTCDoug Daniels

Hmmm.... if the "last layer of clay" isn't affected by a spot cleaning gun, then I'd be wary of a chemical treatment. Then again, test it on an inferior specimen first. Better to be a bit ugly than totally ruined (and to me, the way that specimen looks isn't all that bad - it shows it's formation environment, something us more scientific geeks like to preserve when possible).

14th Sep 2018 06:06 UTCWayne Corwin

Like Doug said... "Hmmm.... if the "last layer of clay" isn't affected by a spot cleaning gun," then Hmmmm... maybe it isn't clay?

14th Sep 2018 08:41 UTCMark Heintzelman 🌟 Expert

Here in Pennsylvania we have quite a number and variety of Limonite pseudo after Pyrite localities, some found floating in heavy clay soil, others still attached to the original but now decomposing host rock, which is what you have there.

In some cases they separate cleanly with moderate physical force, in other cases if the host rock is not weathered enough, they won't separate without significant damage. At several of these localities you have both pseudos in decaying matrix and deeper, the original unaltered pyrite in unaltered host rock (phyllite schist). These unaltered crystals are very difficult, often impossible to part undamaged from the matrix to begin with. These issues are common at the Chestnut Hill locality. Either you leave them as found or damage them . . that's your choice.

See: https://www.mindat.org/loc-69069.html

14th Sep 2018 09:37 UTCDale Foster Manager

Doug Daniels Wrote:

-------------------------------------------------------

Better to be a bit ugly than totally ruined (and to me, the way that specimen looks isn't all that bad - it shows it's formation environment, something us more scientific geeks like to preserve when possible).

I would agree with this.

Looking a the pictures of your specimen I would be inclined to remove only as much as can be safely picked off, then just give it a final wash and leave it.

I rather like the fact it shows some context of the environment it came from.

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