Blotches on Walnut end grain

[ArborGloria]

 

 I am sanding down a piece of Walnut. The end grain has some dirty blotches that won't sand out. Can anyone identify what the blotches are and advise how to get rid of them. I suspect it might be mould but thought I would be able to sand through it.  Any suggestions?

 

[WDH]

Are they burn marks from a saw blade?  It looks like that could be it, and if it is, it will sand out with much time and effort on your part.  That is where a drum sander will save your bacon.  

[GAB]

Are they burn marks from a saw blade?  It looks like that could be it, and if it is, it will sand out with much time and effort on your part.  That is where a drum sander will save your bacon.  

WDH:
Congratulations!  This has to be a record.  Got to food in a non-food thread in the first reply.
GAB

[WDH]

I try.  

[metalspinner]

A drum sander will burn it, too. Need to start with a course grit and enough  feed speed to keep the heat down. 

[ArborGloria]

Sadly not burn marks.  I have taken it down 2 to 3 mm using 40 grit on an orbital sander and there is no change.  I fear it could be diseased or mould.  I have heard bleach could rid it if its mould but don't want to risk tainting the whole piece.

[kantuckid]

If it's not burn marks or mold I've never seen that in lots of walnut I've sawn and used in my shop? 

Why would mold permeate all the way through the wood?

[ArborGloria]

I've no idea.  I can only guess that mould got to it in the curing process and because it the end grain it has managed to work its way deep into the wood. Could it be diseased?