Moonstone? Fire opal? Please help!

Hello, I purchased this lovely piece thinking it was a moonstone. I have never had a moonstone before and forgot to ask about - I was simply attracted to it. The first night, I placed it next to my bedside and I had awful nightmares which I rarely have nowadays (thank goodness). When I visited a crystal shop today, the associate insisted that it was definitely not a moonstone and was a fire opal and they would know since they work with them. When I got home, I looked up fire opals and got even more confused since the majority I found were pretty red and orange colors. This stone is almost clear with not a lot of patchy rainbow colors at all. Now I’m more confused than ever. It could be, but I have a real opal with vivid play of colors and the patterns don’t seem to be the same. I would love your input, thank you all in advance for your help!