Valuable Residue in Wood Ash?

Howdy Any and All: I sometimes discover little nuggets in the ash after my masonry heater fires. The nuggets are popcorn-like but smaller and a distinct green--the colour of oxidized copper. Is it copper? I burn 90% hardwood with cedar kindling. This maybe isn't the best forum for this question, but I didn't know where else to put it. Maybe I could include a photo if I can find some more of the substance, but as this is only my second post ever, I don't even know how to do that! Thanks.

The main question I have is what is the source? Is this wood all stuff you cut and split yourself? Can you grind apart the popcorn?

If it is only these nuggets you are worried about, then you might use a sieve to remove them from the then more acceptable ash.

HI Ron: Thanks for the reply. I'm not worried by these nuggets--I've noticed them for years. They'd be tough to sift out because they're a similar size to some of that charcoal chunks. You can pretty easily squish these nuggets into powder with your fingers. The source for my firewood is all local trees growing above limestone bedrock. I'm thinking the substance is inherent to the trees, but I have not been able to correlate it to a particular species. We have trees similar to what you do in N.H. I burn a lot of maple, ash, beech, some elm, hop hornbeam.