Cleaning Rock

[RJB]

  Hello everybody out there in fossil land.  I am getting a huge slab of rock ready for prep and after yesterday, cleaning, scrubbing and washing the surface, I am left with an awful stain on the rock.  Just wondering if it is there for eternity or can it be cleaned?  I was thinking bleach but didn't want to try it and ruin the rock?

 

RB

 

Here is the slab.  You can easily see all the dark/black staining. 

[Fossildude19]

Why not try the bleach on a small area you are going to cut off, anyway?

[ynot]

What type of rock? Where is it from? How deep does the stain go?

[Jaybot]

If it is some sort of algae staining, hydrogen peroxide has worked for me in the past.

[FossilNerd]

I don’t have a clear answer but maybe food for thought...

I know bleach works pretty well on algae and mold that grows on the siding of a house, but I have no experience with using it on fossils. Maybe try it on an inconspicuous area?

 

I’ve heard of people using chemicals like CLR or Iron Out on mineral staining, but I doubt they would do much on something like algae or ground in dirt.

 

Any idea what may have caused the staining?

[Doctor Mud]

Bummer- last thing we want when cleaning rock. For it to make it worse 

 

Weird - has the water drawn something out of the matrix to the surface or wet it?

 

Peroxide might work. But it does dissolve carbonates. I’ve used it to process forams.

Id use peroxide not chlorine bleach if going down this route. 
I’ve been cleaning some bones and they warn against using chlorine bleach as a rinse in water won’t neutralize it and it will keep on reacting. 

[Doctor Mud]

It looks quite superficial around the edges. So it is only on the surface?

[FranzBernhard]

Looks like some minerals have been deposited in a bedding-parallel crack? 

Air abrasion could work. Or just leave it alone - maybe some good contrast after prepping the thing?
Franz Bernhard

[RJB]

Wow!  Thanks for all the responses everybody.  Looks like I will be trying hydrogen peroxide on the edge and see if that does anything.  Its just a mother nature stain and once the specimen is all prepped out I dought anyone will notice the stain, but if I can get it to look even a little bit better,,,,,,,,,,,,  Wish me luck

 

RB

 

[Jaybot]

8 hours ago, Doctor Mud said:

they warn against using chlorine bleach as a rinse in water won’t neutralize it and it will keep on reacting. 

That's what I've heard as well.  Apparently bleach can eventually ruin modern skulls after a few years due to that.

Not sure how that would affect shale/limestone though

[RJB]

Hey everybody.  I tried hydrogen peroxide yesterday about 5 times in the same little spot all the while scrubbing with a toothbrush and not being able to tell if it did anything, I'm going to just leave it at is.  Thanks for trying everyone.

 

RB

[Wrangellian]

I was going to ask what kind of stain is it and what did it look like before washing? I don't know what it will look like once prepped but if it's a natural stain, may as well leave it, it doesn't look too bad (unnatural) to me.