Are there any manmade opals or simulants?
Many people get confused over the difference between a simulant or an imitation gemstone and a synthetic or lab-grown gemstone. While a simulant looks more or less (sometimes a lot less) like the natural material, a synthetic gemstone is a manmade equivalent of a natural gemstone with essentially the same chemical constitution and physical properties as the natural product. Most gems have been imitated or simulated fairly successfully with glass for literally millennia: the Roman historian Pliny complained about it just slightly over 2,000 years ago. However, a successful glass imitation of precious opal is a much tougher nut to crack. Imitations of precious opal made of milky glass and scraps of tinsel may make fun beads but are so unconvincing as opal as to be hardly worth mentioning as a serious simulant. Fire opal can be plausibly imitated by a slightly cloudy orange, yellow, or red-colored glass, but careful examination under magnification of these imitations usually reveals tell-
