Lol! I poured a fair amount of beads out of the dryer that were loose. They weren't crumbly at all. The rocks in my hand were in between the dryer and condenser before the dryer screen so I can't imagine that material traveling through the cap tube, evap, comp, & condenser to accumulate there. Cap tube cleared up about 6-8" up. Also it was very dry, no sign of oil whatsoever. Compressor still running quiet though. It's a 134a system and the condenser had enough wool on it to knit a sweater!
A friend of mine had an employee of his working on a lawyer's package unit. He was changing out the compressor and installed the LL dryer on the hot gas line. It ran fine for 2 or 3 months before the dryer came apart inside and stopped up the system. The material in your system looks like desiccant beads to me.