Classifying your concentrates into very narrow size cuts makes the separation of even 400 mesh heavy metal powder from rock particles easy to do with a pan, blue bowl, miller table, or similar device. This handy little classification tool is used on thoroughly dried material only. However, the collection of fine abrasive dust on the plastic threads of this tool creates friction that can easily lead to cross-threading of the relatively soft plastic pieces. Screw the threaded containers and ring together gently; brute force will lead to damaged parts. If the friction gets too intense, stop and wash the parts clean before thoroughly drying them and resuming your work. Do that, and this classifier should have a long and profitable life.