My Boyfriend Just Peed In A Glass Cup To Look

My boyfriend just peed in a glass cup to look at his pee, to check it. he was concerned because sometimes lately, it is painful for him to pee. his pee was dark yellow, didnt look like bloody pee, and looked normal at first, just dark yellow. but after a few seconds, we saw brown dust like particles on the bottom, floating around and going to the top. it resembled paprika or cinnamon. there hasnt been any blood from his urethra. could this be broken up kidney stones? he said hes had them before, but never debris in his pee like this. could it be something serious? also last night, his back gave out where he hurts intensly to walk, and has to use my dads old walker to help him. could the kidney stones powder (if thats what it is) and his horrible back pain be linked?