Trust your first thoughts, set aside second thoughts as those are doubts settling in. From my experience with working with stones and pendulums, this is always the best approach. First thoughts are your intuition talking to you. Second thoughts usually cloud the message(s) that are coming through. So best to set those gently aside and as always, trust in your first feelings, thoughts, imagery, etc. If its negative, it may be that the crystal could do with cleansing. You can try asking the crystal which method it prefers but if no answer, then full moonlight would work just as well. Only go with what sits right with you and your tool, of course, only if you feel drawn to clear it as well.