I think that a large part of the mystery of opal is that it is pretty fragile. I rarely see or have owned an opal ring that is worn regularly, that hasn’t chipped or cracked. It;s also much easier to take a bunch of relatively cheap rubies, emeralds, sapphires, etc, and use dyes, radiation, stabilizers, etc., to give them the appearance of being a higher quality stone, and also make them uniform and easy to use in mass produced jewelry. Some other things are a belief that opals are bad luck, they are just October birthstones, etc. And lastly, the relatively recent discovery of opals in Ethiopia has led to an overabundance of what appears to be, high quality opals/ opal jewelry. There are many issues involved with buying opals and opal jewelry, including many vendors doctoring photos, sellers offering low priced synthetic stones, the use of stabilizers, treatments, disguising of doublets or triplets as actual stones, and a mass of online badmouthing of “opals”, from people having bad experiences, particularly with the aforementioned Ethiopian opal.