Impure Senntisten crystal are items found in The Empty Throne Room. They are mined from the crystal formations around the throne room (eastern side, not far from the cycles). Mining them requires level 65 Mining, and grants 4.6 experience per ore - or 46.8 if the crystal formation is Empowered. The crystals should be deposited in the Refinatrix in the center of the throne room for an additional 20 experience per crystal.