There are two routes to go here:

Science route: kidney stones are largely made of calcium, oxalate, urate, cystine, xanthine, and phosphate in our world. Presuming dragon physiology is roughly the same as our world, there’s nothing inherently special about these elements in game. Short of “reliquary” type of usages (think finger bone of a saint), there’s no reason to think it is special. Considering dragon scale is used in armor, I have to assume any less exciting dragon “parts” would pale in comparison. Might have value as a trade good or interesting conversation piece to the right collector.

Fun route: this chunk of phosphorus can be used 1d8 times in place of normal phosphorus from your material components pouch, upping the damage die of any [fire] spell cast using it.

tried not being a grumpy godless commie?

You know you’re in Lemmy, right?

I always cut my frozen pizzas into eighths. I eat the whole thing in one sitting either way, but I prefer smaller slices.