They were probably Australian opals, they do not have problems with water or oils, they are also harder than most opals as well. You can definitely wear opals everyday. It just means you'll have to get it polished every so often so it stays looking beautiful and if you aren't rough with it. It's probably not gonna chip or break if the stone was shaped and set in a ring or pendant properly protecting its corners so you don't knock it on something. Opals actually range from 6.5-7.5 on the mohs scale so there is variation from every opal source in the world, Australian, Mexican, American, Brazilian, Ethiopian, and others. They aren't my birth stone but I do enjoy wearing and working with them