Crinoid Matrix Removal

[Lucid_Bot]

Howdy! I found dozens of crinoid stems recently and most of them seem to have a thin layer of matrix attached. They were found in limestone, but I don't even know what mineral they've been fossilized in...calcite? Would I be able to remove the matrix with sandpaper and perhaps even polish them? Would sanding them remove visible segmentations? All help is appreciated, thank you.

[Ptychodus04]

Sanding will remove all surface features. Polishing them will do about the same thing. You have to decide if you want a decorator piece or a collection piece. If it's a decorator piece, sand away. If not, you want the least invasive prep possible. You can test the acid resistance of the crinoid by dropping a bit of vinegar on the exposed edge of the crinoid. If it doesn't bubble, you can submerge them in vinegar for a gentle acid prep.

[rocket]

sometimes, but it really depends of the matrix (needs to be tonminerals inside or marl) you can use KOH (Kaliumhydroxyd) with a little bit water. This could clean the surface if the stems are not deep inside the stone. According to your findings I think it is perhaps possible with the stones where you can see the stems on the surface.

Edited November 7, 2022 by rocket

[Ludwigia]

Another possibility if the matrix is not all that hard would be to scrub the crinoids firmly with a steel brush under running water. All you need for that is some "elbow grease".