Is there any use for used lava rocks?

I have a bag of lava rocks, used in a propane grill for about a year. Are the good for anything, soil wise? Are the harmful? Any useful suggestions?

lava rocks are great.. they have a paramagnetic property..also..they are light weight
one thing.. if they are from a grill.. i would be careful if lighter fluid was on them???

If the lava rock has had grease, or (as tropicalnut777 pointed out) lighter fluid on them, I would not think they would be a good addition to a garden.

I think the grease would make them pretty nasty. You don't need lighter fluid for a propane grill.
If you bury them (throw them out back under a bush) for a year then dig them up they might wash off. But are they attractive anyway?

You can always burn off grease by getting a wood fire going hot, then lay the lava rocks on top of the coals thinly enoguh that you don;t smother the fire. Heat plus air will reduce anything organic to coke.

Things go better with coke!

I would crunch them up and b ujry them as water-holding fine gravel or coarse grit..

Yeah, I can see it as potentially a mildly beneficial filler in soil, after cooking off the grease. If you really want to bother. If you want to reduce your landfill impact.

>> If you really want to bother.

That's a good point!

Both time and money are limited resources, so the fact that it would free might not outweigh the fact that it would take hours to get it really clean.

Hmmmph, we just bury stuff near a fire ant mound, they will work over anything left that might be edible, just be careful getting them back out of the dirt later,

I was starting my fall clean up when I found the above mentioned lava rocks and remembered I posted this question! Thanks for the suggestions. I have a shallow hole near one of my arbs so I'll probalbly use them for fill. I don't mind feeding any tiny critters as its far enough from the house. I'll have to look up up paramagnetic properties, Tropicalnut, maybe there is something better for them than fill.