matter widely discussed on forum with various procedures and yields. use search and spend few days studying. also this is not appropriate section on forum for your question.
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=34&t=1494&hilit=fiber+cpu
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=34&t=4383&hilit=fiber+cpu
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=34&t=1408&hilit=fiber+cpu