“Is this real opal, or is it one of those aurora ones?” is a question I hear more often than you would think, usually from someone holding up a listing on their phone. Aurora opal, galaxy opal, rainbow opal: none of those are grading terms any gemologist would use. They are names sellers picked because they sound good, and behind that one name you will find genuine stones, honest trade terms wearing a prettier label, and, a fair amount of the time, no opal at all.
Aurora, galaxy and rainbow opal are not official opal types
Opal is sorted by real, defined categories, the ones I walk through in my full guide to understanding opal: body tone, where the color sits on the black-to-white scale I cover in dark opal and the body tone scale; origin, like Australian or Ethiopian; and form, whether a stone is solid, boulder, or an assembled doublet or triplet. None of that vocabulary includes the word aurora, galaxy, or rainbow. Those three showed up in listings because they evoke the right feeling, wide bands of color moving across a dark background, and there is no trade body policing who gets to use them. One seller’s aurora opal is a genuinely fine natural stone with unusually broad, full-spectrum flash. Another seller’s aurora opal is dyed glass. Same word, two entirely different objects.
What sellers usually mean by the name
Strip away the marketing and the label tends to point at one of three things: an opal with an especially wide, saturated play-of-color that reads as a sweep rather than scattered flashes; an opal with a dark, almost galaxy-like body punctuated by bright pinpoint flecks, a little like stars against a night sky; or, on cheaper marketplace listings, simply the prettiest word the seller had on hand for a stone with no real connection to any of that. The name alone tells you nothing about which of the three you are looking at, which is exactly the problem.
Want a stone you know is genuine? Browse the handcrafted opal rings in my collection, cut and set by hand from opal I buy myself, or ask me about a custom piece.
Why “galaxy opal” jewelry online is often not opal at all
This is the part worth being blunt about. A good share of what turns up under galaxy opal or aurora opal in a marketplace search is resin cast with mica powder or foil to mimic a starry, color-shifting surface, with no silica and no play-of-color physics involved. Some of it is opalite, a man-made glass with a milky glow that borrows opal’s name and nothing else, a distinction I go through in more detail in what actually is an opal. None of that makes it worthless costume jewelry, plenty is well made and sold honestly once you know what it is, but it is not a gemstone and should never carry a gemstone price. The GIA’s opal reference is a good baseline for what genuine precious opal is structurally: silica spheres holding trapped water in a disordered arrangement, which is the physical reason real opal flashes color at all. Resin and glass do not do that. Any shimmer they show comes from added glitter, foil, or a dye job, not from light splitting between silica spheres.
How to tell what you are actually holding
A few checks catch most of the imitation material before money changes hands.
- Ask what it is, plainly. Natural solid opal, doublet, triplet, lab-created, or not opal at all. A seller who cannot answer directly is telling you something.
- Look for true play-of-color, not fixed shimmer. Real opal flashes and shifts as you tilt it. Painted or foiled imitations show a pattern that barely changes with angle, because the color sits on a surface instead of inside the stone.
- Check the price against the size. A large, vividly colored stone priced under an hour of a cutter’s wage is not natural opal.
- Ask about hardness and care. Natural opal sits at 5.5 to 6.5 on the Mohs scale and needs gentle handling, no soaking, no ultrasonic cleaner. A seller who calls their aurora opal tough or scratch resistant is very likely describing glass or resin.
The real phenomenon behind the name
There is a genuine version of what these names are reaching for. Most precious opal flashes in patches of one or two colors, blue and green most commonly, with orange and red rarer and more valuable. Every so often a stone shows color across the whole visible spectrum at once, red through violet, moving together as one sheet rather than separate flecks. Cutters sometimes call that full-spectrum or rainbow play-of-color, a genuinely rare, sought-after trait in natural opal, the kind of stone that makes you stop and turn it under the light a second time. It sits alongside the other uncommon patterns I cover in my guide to rare opal varieties. That is the real thing the aurora and rainbow names are borrowing from, and it comes down to how the silica spheres inside that particular stone happen to be sized and packed, not to resin or foil.
What I look for at the bench
When rough or cut material crosses my bench described with one of these names, I ignore the label and grade it the way I grade anything else: body tone, brightness, pattern, and how much of the spectrum actually shows. The best full-spectrum stones I have handled came out of dark-bodied Australian material, the same ground that produces the black opal from Lightning Ridge, because a dark body is what lets that much color read at full strength. A stone with true full-spectrum flash earns its price on those merits alone, no marketing name required. If a piece turns out to be glass or resin once I look closely, I say so, because a customer deserves to know what is going into a ring before it is set, not after.
Part of why sellers reach for a name like aurora or galaxy is that opal has always carried a bit of wonder around it, the same pull I write about in the meaning of opal. A real stone does not need a borrowed name to earn that feeling. If you are shopping for one with genuine, wide-spectrum color, judge it on body tone and pattern rather than whatever name is on the listing, and buy from someone willing to tell you plainly what you are getting. Browse the opal rings and opal pendants in my current collection, every stone cut and set by hand from material I bought myself, or get in touch and I will help you find one that earns the name on its own.
Richard Lewis has worked at the jeweler’s bench for more than fifty years. He trained at the Revere Academy of Jewelry Arts in San Francisco and makes each piece in this shop by hand in his Santa Rosa, California studio. His specialty is natural opal and rare abalone pearls collected off the Mendocino coast over thirty years. More about Richard.