Too perfect. Patterns look "snakeskin" or repetitive.
Transparent. Colors look like they are floating. Check the Construction Not all opals are solid pieces of stone. Solids: 100% natural opal. Best for investment. Doublets: A thin slice of opal glued to a dark backing. Triplets: Opal slice with a clear quartz/glass cap. how to buy opals
Tiny cracks on the surface. These can eventually break the stone. Too perfect