Pyrite

Hi all
My daughter is becoming quite interested in geology and we bought her a little box of different stones which she has been really fascinated by.
The pyrite has started to break down, like its melting and going greasy. Were wondering why this would be and havent been able to find anything online so far. Im thinking it might not actually be pyrite but she tells me that pyrite is worthless and plentiful so she doubts that the people who put the box together would bother substituting it for something else. Any thoughts?

Welcome to P.A.

I could understand if it was oxidising but melting? Is it producing any heat?

She is correct - why not get her a better piece? Hard to tell but it does not look much like pyrite.

A good place to get cheap specimens is sometimes Museum shops (eg Melbourne Museum)

Thanks for the responses.
No it doesn't seem to be creating any heat. It's just starting to break up into pieces and there's a white greasy looking substance coming out of it.
Yes I think she does need a better piece. We'll keep an eye out. At the moment though she's intrigued by what's happening to it so it's pretty cool in that regard.

Pyrite - you can buy this sort of thing at museum stores as a rule - a lot cheaper than on-line dealers.

Make sure she washes her hands after fiddling with the pyrite ..... decomposing pyrite can release arsenic.
Better to be safe than sorry (although the small amount would be much of a hazard).
Cheers T.