Gemstone profile and identification guide
Moonstone is recognised by light that seems to float just beneath the surface. That soft billowing glow gives even simple cabochons an internal life that is very different from the brilliance expected in faceted transparent gems.
Moonstone is recognised by light that seems to float just beneath the surface. That soft billowing glow gives even simple cabochons an internal life that is very different from the brilliance expected in faceted transparent gems.
Did you know? The classic moonstone effect depends on light scattering between intergrown feldspar layers inside the gem.
Use this profile as a collector reference and educational guide for quick on-page comparison, then validate with the interactive identification system.
Name: Moonstone
Scientific classification: Feldspar (Orthoclase/Albite Intergrowth)
Hardness: 6 Mohs
Transparency: transparent to translucent
Lustre: vitreous to pearly
Crystal system: Monoclinic (orthoclase host)
Primary colour: Green
Secondary colour: Brown
Colour family: Greens
Look for adularescence moving across a domed surface, usually in cabochon cuts. It differs from opal because the effect is a floating sheen rather than broken spectral patches, and from glass because the glow appears structured within the stone.
Status: verified-core-fields
Reference priority: GIA, Gem-A, Mindat, International Gem Society
Core identity fields reviewed against consensus gemological references (GIA/Gem-A/Mindat/IGS).
Some market- and locality-level details may still require citation-grade source notes for publication workflows.
Hardness category: medium
Hardness value: 6 Mohs
Chemical composition: Potassium aluminum silicate with albite intergrowths [(K,Na)AlSi3O8]
Crystal system: Monoclinic (orthoclase host)
Common locations: Sri Lanka, India, Madagascar, Tanzania, Myanmar
Learn more: Gem-A gemstone education resources.
Moonstone sits in the greens grouping here, usually reading first as green with brown appearing as a secondary note or modifier. Some specimens also show opalescence, iridescence, which can alter the way the colour is perceived under changing light.
Optical effects: Adularescence
Mineral species: Feldspar intergrowth (orthoclase/albite)
Mineral group: Feldspar group
Chemical formula: Potassium aluminum silicate with albite intergrowths [(K,Na)AlSi3O8]
Mohs hardness: 6
Crystal system: Monoclinic (orthoclase host)
Lustre: vitreous to pearly
Transparency: transparent to translucent
Streak: White
Cleavage: Perfect in two directions
Fracture: Uneven
Specific gravity: 2.56-2.74
Refractive index: 1.52-1.57
Optical phenomena: Adularescence
Colour range: Green, Brown
Common inclusions: Lamination, cleavage traces, and internal growth textures
Geological environment: Moonstone occurs in Igneous and metamorphic feldspar-bearing host rocks. Its Monoclinic (orthoclase host) structure reflects the pressure-temperature conditions of those host rocks, with notable occurrences in Sri Lanka, India, Madagascar, Tanzania, Myanmar.
Principal mining regions: Sri Lanka, India, Madagascar, Tanzania, Myanmar
Important commercial sources: Major gem-quality moonstone sources include Sri Lanka, India, Madagascar, and Tanzania
Historical significance: Feldspar gems are long-used ornamental stones, especially moonstone and labradorite varieties.
Common treatments: Generally untreated; coatings and dyed imitations may appear in low-cost products.
Synthetic or imitation forms: Glass and coated simulants are common for optical-effect imitations.
Common look-alikes: topaz, peridot, tanzanite
Jewellery uses: Moonstone is used chiefly for A good fit for collectors and jewellers looking for visible character without needing the highest hardness category.. In the trade it is commonly fashioned as faceted stones, calibrated cuts, and higher-clarity collector pieces, with Mohs hardness 6 guiding suitable jewellery applications.
Care recommendations: Moonstone should be cleaned with lukewarm water, mild soap, and a soft brush. At Mohs 6 in the Monoclinic (orthoclase host) system, avoid steam cleaners, harsh chemicals, and high-impact wear. Protect cleavage directions from sharp knocks during wear and setting.
Cross-check profile data with GIA Gem Encyclopedia and Mindat entry for Moonstone.
Moonstone is a Feldspar intergrowth (orthoclase/albite) material with chemistry Potassium aluminum silicate with albite intergrowths [(K,Na)AlSi3O8]. It develops in Igneous and metamorphic feldspar-bearing host rocks, and economically significant production is associated with Sri Lanka, India, Madagascar, Tanzania, Myanmar.
Major gem-quality moonstone sources include Sri Lanka, India, Madagascar, and Tanzania
Best for: Moonstone is used chiefly for A good fit for collectors and jewellers looking for visible character without needing the highest hardness category.. In the trade it is commonly fashioned as faceted stones, calibrated cuts, and higher-clarity collector pieces, with Mohs hardness 6 guiding suitable jewellery applications.
Ideal uses: A good fit for collectors and jewellers looking for visible character without needing the highest hardness category.
Moonstone should be cleaned with lukewarm water, mild soap, and a soft brush. At Mohs 6 in the Monoclinic (orthoclase host) system, avoid steam cleaners, harsh chemicals, and high-impact wear. Protect cleavage directions from sharp knocks during wear and setting.
Need another candidate? Use advanced gemstone search or return to the identification guide.
Compare hardness (6 Mohs), crystal system (Monoclinic (orthoclase host)), colour profile, and lustre (vitreous to pearly) with your sample. Then cross-check related gemstones listed above.
Moonstone sits in the greens grouping here, usually reading first as green with brown appearing as a secondary note or modifier. Some specimens also show opalescence, iridescence, which can alter the way the colour is perceived under changing light.
A good fit for collectors and jewellers looking for visible character without needing the highest hardness category.. For maintenance, follow the care guidance in this profile.
GIA: general gemstone identity (reviewed) - Reviewed as a direct core gemstone profile.
Gem-A: gemological education and terminology (reviewed) - Reviewed as a direct core gemstone profile.
Mindat: mineral species and locality index (reviewed) - Reviewed as a direct core gemstone profile.
International Gem Society: collector-facing gem reference (reviewed) - Reviewed as a direct core gemstone profile.
