- Jewelry Identifier
- Gemstones
- Moonstone
* feldspar (orthoclase + albite) gemstone
Moonstone: identification, value, and how to spot a fake
Feldspar with characteristic adularescence (billowy blue-white sheen from layered orthoclase/albite). Sri Lankan blue moonstone is the premium. Rainbow moonstone is actually labradorite from India.
Published May 30, 2026
Quick facts
- Mineral family
- feldspar (orthoclase + albite)
- Chemical formula
- K(AlSi3O8) + Na(AlSi3O8)
- Mohs hardness
- 6–6.5
- Refractive index
- 1.518–1.526
- Specific gravity
- 2.56–2.62
- Crystal system
- monoclinic
- Luster
- vitreous, pearly on cleavage
- Birthstone month
- June
Colors
Moonstone is found in white, blue, rainbow, peach, gray. The body color, its saturation, and how evenly it spreads through the stone are among the strongest drivers of value.
How to tell real from imitation
No single test settles it, but a few grounded checks quickly narrow things down for Moonstone. Hardness, brilliance, and the list of stones it is commonly confused with all give you something concrete to look for.
- Scratch resistance: genuine Moonstone sits at Mohs 6–6.5, so it should resist scratching from softer materials — a stone that mars far too easily is suspect.
- Brilliance & luster: Moonstone shows a vitreous, pearly on cleavage luster and a refractive index of 1.518–1.526; imitations often look glassier or flatter under the same light.
- Density: a real Moonstone has a specific gravity near 2.56–2.62, so it feels heavier or lighter in the hand than many look-alikes of the same size.
- Commonly imitated by: chalcedony, milky quartz, opal. If a deal looks too good, suspect one of these substitutes first.
- Fast first read: photograph the stone in the Jewelry Identifier app to estimate the gemstone and its likely value range, then confirm anything important with a gemological lab.
Common treatments
- none typically
Treatments are routine for many Moonstone stones, but they materially affect value and should always be disclosed — an untreated, lab-certified stone commands a clear premium over a treated one.
What to know about Moonstone
Feldspar with characteristic adularescence (billowy blue-white sheen from layered orthoclase/albite). Sri Lankan blue moonstone is the premium. Rainbow moonstone is actually labradorite from India.
Sources
* Frequently asked
FAQ
- Q. Is Moonstone hard enough for everyday rings?
- A. Not ideally. At a Mohs hardness of 6–6.5, Moonstone is soft enough to scratch with everyday wear, so it is better suited to earrings, pendants, or occasional-wear rings with protective settings.
- Q. How can I tell Moonstone from chalcedony?
- A. Moonstone and chalcedony can look alike to the naked eye, but they differ in measurable properties — refractive index (1.518–1.526 for Moonstone), specific gravity (2.56–2.62), and hardness (Mohs 6–6.5). A gemologist confirms the distinction with a refractometer and loupe; the Jewelry Identifier app gives a fast first read from a photo.
- Q. Does Moonstone come in colors other than white?
- A. Yes. Moonstone occurs in white, blue, rainbow, peach, gray. Color is driven by trace elements and treatment history, and it is one of the biggest factors in a stone's value.
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