Clinkers in a wood stove? Or sintered ash?

My clinkers just look like gray volcanic rock, no color. They appear when I burn Black Locust.

What are you burning ? That green looks like copper , are you burning any construction drops ? Even when burning coal I’ve never had clinkers so hard ( I’m thinking silica impregnated wood. It’s not green like Acq or older CCa treated lumber it May form glass like clinkers ( it’s definitely not pressure treated as I’ve seen that burned and it will leave multicolored ashes sometimes the ash will maintain the original shape but will collapse once touched )

I think the consensus here is that the clinkers you are seeing are minerals that were in the wood. At least that's what I've read in the past.

Isaac Carlson said:

That’s a lot of mineral. The green ones look like solid glass, but foggy.

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Someday, perhaps a decade from today, your now-teenage son will tell you he used to toss Molson bottles into the stove to hide the evidence.

Depending on where you get your wood it could be something that was on the tree, like a eye bolt or something, and the tree grew around it and you were fortunate enough not to find it with your chainsaw.

Isaac any possibility of an old insulator having been ingrown in one of the trees ? As in electric fence ? Wood doesn’t create clinkers like that ,

Ash will sinter when heated at high temps. Have gotten ones similar to the one that's fused to your firebrick, I've replaced a couple of them due to that. Mostly though, they're just laying in the ash.

I have not seen them though with the turquoise color (or any color besides white/black). That looks like oxidized copper to me.

I've gotten in the habit of stirring the coal bed a few times when it's burning down. When I do this I get no clinkers. If I don't, I get some.

Isaac Carlson said:

That’s a lot of mineral. The green ones look like solid glass, but foggy.

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If you are burning wood that had been beside a gravel road you'd be stunned at the amount of dirt in the tree. I cut up a Shagbark hickory that was along a gravel road for about 75 years. The amount of grit embedded in the tree was really something, I think I went through about 7 sharpenings just cutting that one tree up.