Hold a good moonstone under a lamp and tilt it. A soft light moves across the surface, like something floating just under it. That movement is why people buy this stone.
The trouble is the name. Two stones can sit side by side with the same label and be two different minerals. GIA says the pale stone sold as rainbow moonstone is a variety of labradorite.
That is not a scam, and the name is normal in the trade. But if you think you are buying one thing and you are paying for another, that is worth knowing first.
I cut moonstone by hand in my workshop in Tbilisi. Below is what the glow is, how to check a stone yourself in a few seconds, and what the gemology sources say. Where something is my own experience at the bench, I say so.
What moonstone is
Moonstone is a feldspar. So is labradorite, and the two are related in a way that matters later: both get their look from layers inside the stone rather than from color.
What makes moonstone moonstone is that it is not one feldspar but two. GIA puts it simply: "It's composed of two feldspar minerals, orthoclase and albite." The two separated into stacked layers as the stone cooled, and those layers are what the light plays on.
| Family | Feldspar, one of the most common mineral groups in rock |
| Made of | Alternating layers of two feldspars, orthoclase and albite |
| Hardness, how well it resists scratches | 6 to 6.5 on the Mohs scale |
| Weak direction | Splits cleanly in two directions |
| How clear it is | Transparent to opaque, depending on the piece |
| Comes from | Sri Lanka, India, Madagascar |
Not all moonstone is see-through
That fifth line is the one most articles skip, and it decides what to expect. IGS gives moonstone's body color as anything "from colorless through shades of yellow, gray, green, pink, reddish, orange, and brown."
The clear stones with a blue sheen are the ones that get photographed and graded. The dense white ones are moonstone too. This article covers both, because they are not competing with each other.
Two lines in that table decide how a piece wears. Moonstone is softer than quartz, and quartz is in ordinary dust. It also splits cleanly in two directions, so one knock can do more damage than years of wear.
The name of the effect comes from a place. IGS traces it to "Mt. Adular in Switzerland, a famous source for these gems." That is where the word adularescence comes from, and adularescence is the proper name for the glow.
Where the glow comes from
The glow is not on the surface. It comes from inside the stone.
Light goes in, meets those stacked layers, and comes back out. GIA describes it: "it scatters in many directions, producing the phenomenon called adularescence." What you see is that scattered light gathering into a soft patch, which GIA calls "the light that appears to billow across a gemstone."
Because the light comes back from inside, the patch travels as you tilt the stone. A reflection of the lamp stays where the lamp is.
One thing follows from this, and the rest of the article depends on it. Light has to cross the surface of the stone before it reaches those layers, so the surface decides what you see. A polished face lets the light gather into that patch. A raw face scatters it at the surface instead, and the stone reads as an even white.
Neither surface is unfinished and neither is damaged. Polishing decides which part of the stone you get to see: the light inside it, or the crystal itself.
What a raw surface gives you
Most moonstone is polished, and for a reason. IGS notes that cutters usually shape it into high domes to bring the sheen out. Leaving the surface raw shows something else instead.
The stone still looks like a stone
A raw face comes two ways in my pieces. On the rings it is a crust of tiny crystal points, the surface the stone grew, and I leave it untouched. On the tapered stones I cut the face myself and stop before the polish, so it stays matte and finely grained. Nothing has been buffed smooth in either case, so what you see is the stone itself and not a finish put on top of it. A polished dome looks like a gem. A raw face looks like stone, held in silver.
The trade-off is real. A raw white moonstone does not give you a moving blue sheen. If that is what you came for, you want a polished translucent stone, and there is a section below on how to buy one. What a raw stone gives you instead is surface, texture and a white that stays the same from every angle.
No two raw faces are alike
Two polished domes of the same size are nearly interchangeable. Two raw faces never are, because the grain and the angles differ in every piece of rough. This is why raw pieces are sold one at a time: the stone in the photograph is the stone you get. The same thinking runs through all of my raw stone jewelry, and my article on pyrite explains why polishing would destroy that stone's flat crystal faces.
How to judge a raw moonstone
Buying guides assume a polished stone. A raw one is judged on different things, and none of them are hard to check.
1. The white itself. Look at the face in daylight and ask whether the white is even. Patchy gray, or a yellow cast in one corner, will bother you more over time than any other flaw.
2. Whether the face is intact. On a crystal crust, look for scrapes and flattened patches, because they cannot be undone. On a cut matte face, look for an even grain with no shiny spots, because a shiny spot means someone started to polish it and stopped.
3. Cracks that run with the split. This is the one that matters for durability, because a crack already running along a splitting plane will keep going. Hold the stone up to a light and look along its edges, not just at the face.
Small internal marks are a different thing, and they are normal. GIA lists "tiny tension cracks called centipedes" as a characteristic of the stone, and those are evidence that it is natural.
4. How the silver holds it. Check that the metal covers the edge of the stone all the way round, because the edge is where a knock lands first.
5. Size against where you wear it. A large stone on a pendant sits still. The same stone on a ring meets door frames, so if you want size, put it where it takes no knocks.
What is not a flaw
In a raw stone these are normal: a matte surface, small pits, a face that is not flat, edges that are not symmetrical, and internal veils. If a seller has removed all of that, you are no longer looking at a raw stone.
How to spot a fake
What is sold as moonstone but is not moonstone falls into two groups: glass, and other stones wearing the name.
A raw face is hard to fake
Glass imitations are poured into molds, and IGS lists what that leaves behind: "mold marks, rounded facet edges, and concave facets", plus "swirl marks and round bubbles" under magnification. Facets are the flat faces cut onto a stone, and on glass their edges come out soft instead of crisp.
IGS names the usual material too: opalite is "a trade name for a type of glass often used to simulate moonstone or opal."
A natural crystal face does not behave like that: the grain runs in different directions and no two areas look the same. Copying that in glass costs more than the glass is worth. So on a raw stone the rule turns around. Perfectly smooth and perfectly even is the warning sign, and texture is the evidence.
If the stone is polished, watch the light move
If a stone is sold on its glow and the glow does not move as you turn it, stop there.
Read the name on the label
Rainbow moonstone is labradorite. Blue moonstone, IGS says, is "artificially blue-tinted chalcedony", a dyed quartz rather than a feldspar. Both names are legal to use, and both are worth a question before you pay.
One more warning sign: a row of beads that are all flawless, all identical and all lit the same way. Natural stones carry small marks.
What I would not rely on
Two tests circulate widely and I use neither. Judging a stone by how cool it feels is the first, because the sources I checked describe heat behavior in ways that contradict each other.
Scratching the stone is the second, and it can damage a stone you do not own yet. If a stone matters enough, no home test settles it. A gemological laboratory will.
If you want the polished kind
If what you want is the moving blue sheen, buy a polished translucent stone on these four points. GIA publishes them, and they are the closest thing moonstone has to a grading scale.
- Body color. "Bodycolor should be nearly colorless and free of any yellowish, brownish, or unattractive green tints."
- Color of the sheen. "Adularescence should, ideally, be blue."
- Where the sheen sits. "The sheen should be centered on the top of a cabochon, and it should be easily seen from a wide range of viewing angles. If a moonstone's adularescence is only visible within a restricted viewing range, its value drops."
- Transparency. "A good moonstone should be almost transparent and as free of inclusions as possible."
The third point is the one to use in a shop: hold the stone at arm's length and move it slowly through a wide arc. A glow that only appears in the seller's lighting will do the same on your hand.
I do not cut this kind. My stones are raw and white, which is a different thing to want.
Rainbow moonstone is labradorite
This surprises most buyers. The pale, glassy stone with flashes of color, sold everywhere as rainbow moonstone, is not moonstone in the mineral sense. GIA says it plainly:
It "has a multicolored adularescence over a light bodycolor. It's known in the trade as rainbow moonstone, despite the fact that it's actually a variety of labradorite rather than orthoclase." (GIA)
Nobody is hiding this. The name describes the look rather than the mineral. GIA spells out the rule behind it: "To be called moonstone, a mineral's actual identity is not as important as the beauty of its adularescence."
In the hand the difference is simple. Classic moonstone is close to colorless, and the light coming off it is blue or white. Rainbow moonstone is clearer, and its light carries several colors at once over a pale body color. Neither is better, but they are different minerals at different prices, so it is worth knowing which is in front of you.
If you want the other one, it sits under its own name in my labradorite jewelry.
What moonstone means
Moonstone is tied to the moon in nearly every tradition that used it, and it is one of the June birthstones.
GIA records the oldest version: "According to Hindu mythology, moonstone is made of solidified moonbeams." These are traditions, recorded as traditions rather than as properties anyone has measured. I cut stone for a living and I will not tell you what this one does for your life. If the white and the texture make you want to wear it, that is reason enough.
One part of its history can be checked. GIA notes that "great designers of the romantic Art Nouveau era, such as René Lalique and Louis Comfort Tiffany, featured the pale gem in custom jewelry."
Looking after moonstone
GIA's care page puts the consequence of that splitting plainly: moonstone "has poor toughness", and cleavage "makes a crystal more prone to breaking". Everything below follows from it.
- Water is fine, soap is enough. GIA: "Warm soapy water is the only recommended substance for cleaning moonstones."
- No ultrasonic or steam cleaners. GIA calls them "never recommended", and that covers most jewelry shop machines, so say what the stone is before handing a piece over.
- Keep it away from sudden heat. GIA: "High heat or sudden temperature change can cause breaks in moonstone." Take it off before a sauna or a hot bath.
- Store it on its own. Most stones in a jewelry box are harder and will scratch it.
- A raw face needs rinsing. A grained surface holds soap and hand cream where a polished one sheds them. Rinse under clean water and dry it properly, because dried soap in the grain shows as a dull patch.
GIA notes that manufacturers usually set moonstone into pendants, earrings and pins rather than rings, because of that splitting. It does not make a moonstone ring a mistake. It means the ring comes off before heavy work. If you want the white with less to think about, moonstone earrings and pendants meet fewer corners than a hand does.
How I cut moonstone at Akra
My workshop is on Abano Street in Tbilisi, in the same place as the shop. Every piece is drawn here, cut by hand here, and set in 925 silver here. My moonstone is the classic kind, orthoclase with a white body, and the rough comes from Sri Lanka. I choose it myself rather than ordering by description.
I stop before the polish
That is the decision the collection rests on. I open the rough, cut the shape by hand, and choose the face that will show. Where the rough carries a good crystal crust, that crust becomes the face and I do not touch it. Where the shape needs a cut face, as on the tapered stones, I cut it and stop before the polish. Either way the work stops before anything is buffed smooth.
It is not the faster route. A polished dome hides small irregularities; a raw face shows everything, so that choice has to be right the first time.
How the silver holds it
The silver holds the stone at its edge and leaves the face open. On some pieces that is a ring of claws, on others a bezel edged with silver beads, and on the branch pieces a frame of twigs that closes around the stone. I darken the silver on purpose, so the white stays the brightest thing in the piece.
For earrings the two stones are chosen side by side, to match in tone and in the angle of the cut. A pair of raw stones has to be built, not picked off a tray.
The current pieces are in moonstone jewelry, including the moonstone necklaces, where a larger stone has room to show the full face.
Quick answers
How can I tell if moonstone is real?
It depends on the finish. On a polished stone, turn it: the glow should travel, while a reflection on glass stays put. On a raw stone, read the surface: a natural crystal face is uneven and grained, while molded glass comes out smooth, often with round bubbles inside.
Why is your moonstone not shiny?
Because I stop before the polish. A polished dome gathers the light into one bright patch. A raw face spreads it across the whole surface and shows the crystal instead. It is a choice about what the stone shows, not an unfinished piece of work.
How hard is moonstone?
6 to 6.5 on the Mohs scale, softer than quartz. The number matters less than the fact that it splits cleanly in two directions, so how a piece is set matters more than the hardness itself.
Can moonstone get wet?
Yes. GIA recommends warm soapy water for cleaning it, and rain or hand washing will not harm it. Sudden heat is the thing to avoid.
Is rainbow moonstone real moonstone?
It is a real stone, but it is labradorite rather than orthoclase. GIA states this directly. The name describes the look, so it is worth asking which mineral you are buying.
What month is moonstone the birthstone for?
June. It shares the month with pearl and alexandrite. If you are buying for a June birthday, my guide on choosing jewelry as a gift covers the rest.
