[Greenbuilding] slate treatment

[tom]

We're reusing some slate countertops in the farmhouse we're  
renovating (actually I prefer 'recovering' or 'rescuing,' as it was a  
neglected mess).  They are a dark grey, almost black color, which I  
understand means they are a little more absorbent and softer than  
other colored slate usually is.  I sanded the surfaces some to get  
the crud and grime off, though there is still plenty of 'character'  
left to them (maybe they used them when they were butchering  
chickens!?).  I kind of doubt we'll do any food prep directly on  
them, but any ideas of what (or if) I should treat them with?  I'd  
obviously like to steer clear of industrially produced sealers.  A  
wipe-down with pure tung oil maybe?
thanks