My daughter is suppose to visit this weekend. I asked her to bring her light. We tried it on a few rocks I have and it didn't show anything. I have some Sodalite and some opal. If I remember we tried the sodalite. I don't remember trying the opal.The opal I have is a type that I got from my father and was told you have to boil it in sugar water to bring the colors out. They arent to bright at the moment. I will have to look that up again. It has been awhile!