Sulphurous patch?

[Yoda]

So I was treating my collections from Betteshanger trip with Paraloid.

 

Noticed that this specimen has this large soft yellow patch. 

Looks like some sort of sulphur compound? 

 

How should I treat this?

Just cover the whole rock with Paraloid?

Or should I remove this first?  

 

[Mark Kmiecik]

I believe it is iron sulfide which is common in Mazon Creek fossils as well. It should not react with Paraloid or acetone so it's mostly a matter of aesthetics. If it doesn't bother you that it's there leave it. If you think the specimen would look better without it then remove it.

[Yoda]

14 hours ago, Mark Kmiecik said:

I believe it is iron sulfide which is common in Mazon Creek fossils as well. It should not react with Paraloid or acetone so it's mostly a matter of aesthetics. If it doesn't bother you that it's there leave it. If you think the specimen would look better without it then remove it.

I am happy to leave it as long as the "infection" doesn't spread

It this sort of thing likely to? 

[Ptychodus04]

6 hours ago, Yoda said:

I am happy to leave it as long as the "infection" doesn't spread

It this sort of thing likely to? 

Not if you seal it with the paraloid. I use vinac to treat fossils with pyrite issues with great results. I would clean off what you can and then treat it.

[Yoda]

4 minutes ago, Ptychodus04 said:

Not if you seal it with the paraloid. I use vinac to treat fossils with pyrite issues with great results. I would clean off what you can and then treat it.

Do I just scrape it away with something sharp?

[Ptychodus04]

1 minute ago, Yoda said:

Do I just scrape it away with something sharp?

use a dental pick or some such tool and pick it off. If it is hard and well adhered, just leave it and seal it with the paraloid.

[Yoda]

12 hours ago, Ptychodus04 said:

use a dental pick or some such tool and pick it off. If it is hard and well adhered, just leave it and seal it with the paraloid.

Thanks, I will give it a go this weekend.