All chakras. One of the significant facts about Tibetan Quartz crystals is that they contain a very powerful "OM" vibration.  These all are double terminated and have black phantoms enclosed within the crystal.  They are truly fabulous.  Tibetan Quartz DT crystals can be placed between to chakras to delete stagnant energy and to activate the two chakras.  Large and Brilliant!  Whoa!!!  Oh, I see a rainbow too!!