Why Is My Petrified Wood Growing Hair?

[JBKrygier]

Hi all,

The "hair" is most likely halotrichite or pickeringite, whitish minerals that crystalize quickly into long hairs as a product of decomposing pyrite. Here in central Ohio it can be found covering exposed Ohio shale (which contains pyrite). A vernacular name is alum or feather alum. Similar "efflorescence" minerals, typically produced by dying pyrite, include melanterite (which is blue-green, also known as copperas) and botryogen (orange).

Yes to keeping the hairy specimens (or anything with pyrite) dry. My coating of choice to limit hairy pyrite is indoor stone floor sealer (which they sell at most home improvement stores). Does not add much gloss, and so far (a few years) the treated specimens seem fine. I can't vouch for what might happen long term, so use with caution.

John K.

[Stocksdale]

Thanks, John. Very informative and helpful.