I set two males on wander, with production wheel on crystal, on both, put them on a Dino leash, they both dropped over 500 Crystal within 30 min... did not use owl pellets. They harvested their own stone.
Gachas are essentially living lootboxes and resource farms. They will eat anything (including stone, wood, or fiber) and turb it into crystals which can drop a variety of resources including black Pearl's, organic polymer, or obsidian, among other things. They also have a rare chance to drop higher-tier crystals which turn into upgraded armor and tools