Maple wood petrifying in smoker?

Asked February 7, 2016, 8:19 PM EST

My fiance recently bought a smoker and has been going to town smoking everything he can think of. He also builds furniture with speciality woods, so sometimes, after researching if it's safe, he puts scraps on the coals of the smoker. Recently, we discovered something strange: anytime we put curley maple into the fire, we would find a rock in the ashes. We also could not find any information on Google about what's happening! Is the wood petrifying? Is this normal? Is it safe to put the curly maple in the smoker if it's doing this? And mostly, why does it do this? Thank you! Erica

Benton County Oregon

3 Responses

Well I must say, you have stumbled onto something quite unusual here. Are you sure they are rocks vs. a charred knot? Sometimes wood will have small pockets of mineral inclusions drawn up from the soil. This usually gives the wood unique colors like green streaks in maple. But these are usually so small that they wouldn't result in forming a rock when burned.

What causes the curly grain figure in maple is generally just repeating undulations in the grain - it's an optical illusion in a way. So there's nothing about the figure in the grain that I can think of that would lead to a rock. Of course, trees grow over inanimate objects like nails or even bicycles such that it's not entirely unexpected that windborne debris like small pebbles caught in a branch crotch could end up buried within the wood.

If you could drop off the rock(s) for us to take a look under the microscope, I'd be glad to see if it is in fact 'animal, vegetable, or mineral.' Well, hopefully not animal...

Hi Scott,

I have a bag of the "rocks" that I'd be happy to send to you via Campus Mail if that works? (What building/office should I send it to?)

I'm positive it's not a charred knot, and they've come from a few different pieces of curly maple we've purchased from a specialty hardwood supplier. They're lighter than a rock, a bit more porous and brittle, and are usually quite a bit smaller than the piece of wood we've put into them. One piece is a fe inches long and at least an inch wide, while others were broken in the smoker's fire and are about quarter size in diameter.

The mystery is driving both of us crazy, so we'd love to hear any theories you have and are happy to answer questions about the conditions under which the "rocks" are produced!


OK, we'll take a look under the microscope. If we see evidence of wood cells (fibers and tracheids, etc.), we'll know it's wood. I guess the other option is 'animal or mineral' which is far less definitive! Maybe another department here at OSU could assist then.

You can send to me in the Department of Wood Science & Engineering, 119 Richardson Hall.