Two feldspars, one name, two different prices
Most of the moonstone sold today is not moonstone. The milky beads with a blue flash in nearly every crystal shop are usually rainbow moonstone, a trade name the gem trade applies to white labradorite, which is a different feldspar with a different optical effect. True moonstone, the stone from Sri Lanka with a glow that drifts across the surface, is a separate purchase at a separate price. Both are honest stones. Only one of them is what most buyers think they are getting, and that difference decides what you should pay.
What moonstone actually is
Moonstone is an alkali feldspar, a mix of orthoclase and albite that cooled slowly enough for the two to separate into microscopic alternating layers. Those layers are the whole point: light entering the stone scatters between them and returns as a soft, billowy sheen that appears to float just beneath the surface, an effect called adularescence. The stone sits at 6 to 6.5 on the Mohs scale, which is mid-range, and it has two directions of easy cleavage. That last detail is the one that costs people money: feldspar does not wear down the way quartz does, it splits along flat planes.
Two effects that look identical in a photograph
Both effects are interference in feldspar, and in a listing photo they are nearly impossible to tell apart. In your hand they behave differently. Adularescence is soft and diffuse, a milky haze with a blue or silver cast that moves as you tilt the stone and never resolves into a hard edge. Labradorescence arrives as a broad, flat flash of color, blue or green or gold, that appears at one specific angle and vanishes when you turn the stone away. If the color shows up only when the piece is tilted to a single position, you are looking at labradorite, whatever the label says.
Which moonstone you are actually being sold
The names in this corner of the market are applied loosely enough that a label describes an appearance, not a mineral. Read the table as a translation rather than a ranking: everything in it gets sold as moonstone, and only the first row is moonstone in the mineralogical sense.
| Sold as | What it actually is | How the sheen behaves |
|---|---|---|
| Moonstone | Alkali feldspar: orthoclase with albite layers | Soft blue or silver haze that drifts as you tilt it |
| Rainbow moonstone | White labradorite, a plagioclase feldspar | A flat blue flash at one angle that leaves when you turn it |
| Peach moonstone | Alkali feldspar colored by iron | Cream to peach body; the sheen is weaker than in white material |
| Black moonstone | Dark feldspar, usually labradorite | Silver or blue flash against a near-black body |
| Grey or silver moonstone | Lower-grade feldspar with a mixed body | Patchy sheen, often only at the rim of the dome |
| Opalite | Man-made glass, no feldspar at all | Even milky glow that does not move or change |
Treatments: almost nothing happens, and that is good news
Moonstone is one of the few stones in a crystal shop that is essentially never treated. Heating does not deepen the sheen, resins cannot hide fractures in a stone this translucent, and there is no routine irradiation. That takes the usual first question off your list; what replaces it is identification, because the risk here is not an enhanced stone but a different stone wearing the name. A coating is the one thing worth watching: a lacquer or film can fake a sheen on glass, and it will cloud or peel over time, taking the effect with it.
Telling moonstone from opalite and glass
Opalite is the standard stand-in and it is glass: uniform, with a glow that is diffuse rather than directional, so tilting it changes nothing. Real moonstone nearly always shows something inside, a cloud or a fine needle, and its sheen shifts as the stone moves. Weight is less help here than it is with garnet: feldspar sits near 2.6 and glass near 2.5, too close to judge by hand. Look instead at the drill holes, which chip on feldspar and stay crisp on glass. The real vs. fake guide runs through the rest of the home tests.
How to check moonstone in under a minute
Most of these need nothing beyond your hands and a lamp, and together they separate the real stone from the two things most often sold in its place.
- Tilt it slowly. The sheen should drift across the surface rather than switch on at one angle.
- Look inside. A cloud, a needle or a faint layer is a good sign; perfect emptiness is not.
- Check the drill holes. Feldspar chips at the hole; glass stays crisp.
- Compare it with glass. Feldspar is slightly heavier, but only slightly, so use this as a tiebreak.
- Check the surface for a film. A coating shows a faint rim at the drill hole and dulls where you rub it.
- Ask which mineral it is. Moonstone and rainbow moonstone are different stones at different prices.
What moonstone should not look like, and what should
Moonstone is common enough that outright fraud is rare, so the trouble is mostly naming rather than faking. These are the four things worth pausing over, and four that should reassure you.
- Red flag: every bead in the strand flashes at exactly the same angle.
- Red flag: the glow is flat and even across the whole surface, and nothing changes when you tilt it.
- Red flag: a coating you can see as a rim around the drill hole.
- Red flag: sold as moonstone with no mineral named, at a price that only fine blue material reaches.
- Good sign: a sheen that shifts as the stone moves, brightest somewhere near the middle of the dome.
- Good sign: some internal cloud or fine inclusion visible in daylight.
- Good sign: a slight difference in tone between beads, the way natural material actually forms.
- Good sign: a seller who says rainbow moonstone when that is what it is, instead of letting you assume.
The sheen is directional, so the cut decides the price
A moonstone cabochon is not cut for brilliance the way a faceted stone is. The cutter has to find the plane of the internal layers and set the dome on top of it, and that decision separates a fifty-dollar stone from a five-hundred-dollar one. A good cabochon puts the sheen in the middle of the dome, where you see it head-on, and leaves no dead patches at the rim. Weak, off-center or absent sheen is not a matter of taste; it is a cutting failure, and it should be priced as one. Two stones of the same size can differ by a factor of ten.
Strands and cabochons: where the money goes
Bead work is where most moonstone is sold, and the gap between strands is wide. Judge the specification rather than the photograph: consistent bead diameter, clean drill holes, no chipped edges, and sheen on more than a few beads. Expect variation in tone between beads, because natural feldspar does not produce a matching set. A strand where every bead flashes identically at the same angle is either coated or glass. An 8 mm elastic strand sits in the $30 to $70 range, and the bracelet guide covers sizing and what to check when the piece arrives.
Hardness, cleavage, and what moonstone survives
At 6 to 6.5, moonstone is soft for a stone you wear, and its cleavage makes it softer in practice than the number suggests: a knock does not round off a corner, it takes a flat flake out of the surface. Treat it as a pendant or an earring stone, or as a ring you wear occasionally and take off before you use your hands. Keep it away from quartz, which will scratch it, and off a sunny windowsill, because pale feldspar dulls over years. The fade guide lists the stones with the same weakness. Cleaning is easy if you skip the shortcuts: lukewarm water, a drop of mild soap, a soft brush, no ultrasonic and no steam. The cleaning guide covers the method and the stones that cannot take it.
What a fair price looks like
These are typical retail ranges for finished pieces rather than per-carat quotes, and they move with metal, size and sheen strength. The point of the table is the second column: once you know which of the two minerals you are holding, the numbers stop looking random. The price guide covers how these ranges are built across the rest of the site.
| Form | Typical range | What you are really paying for |
|---|---|---|
| Tumbled stone or a single bead | $4-$15 | Weight and polish; sheen on one face at most |
| 8 mm beaded bracelet, rainbow moonstone | $30-$70 | Bead consistency and clean drill holes |
| Cabochon pendant in silver | $50-$150 | A sheen centered on the dome, with no dead patches |
| Faceted moonstone in gold | $200-$600 | Transparency, plus a sheen that survives daylight |
| Large fine moonstone, 10 ct and up | $1,000 and up | Rarity, and a report that names the mineral |
June's birthstone, and what that changes
June has two stones, pearl and moonstone, and moonstone is the one people choose when they want something that is not a pearl. Pale blue-white reads as understated, it sits in silver without looking like a compromise, and the old association with moonlight gives you something for the card without claiming anything about anyone's health. Because the sheen is the whole appeal, buy the stone you can see rather than the stone in the listing photo. The birthstone chart lists the traditional stone for every month, and the gift guide covers choosing by relationship.
Buying online, and the one question that settles it
Photographs are unusually unhelpful here, because the sheen depends on the angle and the light the picture was taken in. Ask for a short video with the stone turning rather than a still, and ask which mineral it is. A seller who answers rainbow moonstone is not cheating you; a seller who answers moonstone to both is not tracking the distinction. Then ask the question that settles it: does the sheen move when you turn it? Adularescence drifts and labradorescence snaps on and off, and either answer is fine. A seller who cannot answer has not held the stone in daylight.
