Carbonate
Azurite
Cuā(COā)ā(OH)ā
Tectosilicate (Feldspar)
Moonstone
(Na,K)AlSiāOā
About Moonstone
Moonstone is a variety of the feldspar-group mineral orthoclase, famous for its ethereal glow known as adularescence. This optical phenomenon resembles moonlight shimmering on water and is caused by light scattering between microscopic layers of two different feldspar minerals. It has been used in jewelry for thousands of years and was particularly popular during the Art Nouveau period.
Formation & Geology
Moonstone forms in igneous and metamorphic rocks. Its unique glow is the result of 'exsolution', which occurs as the mineral cools. Two mineralsāorthoclase and albiteāseparate into alternating, paper-thin layers. When light falls between these thin layers, it scatters in many directions, creating the soft, billowy light effect. Thinner layers produce a blue sheen (the most valuable), while thicker layers produce a white or silvery glow.
Physical Characteristics
Moonstone has a hardness of 6 to 6.5 and two directions of perfect cleavage, making it somewhat fragile and prone to breaking if struck hard. It typically has a pearly to vitreous luster and can be transparent to translucent. The most sought-after variety is 'Rainbow Moonstone', which is technically a variety of labradorite that shows a multi-colored sheen.
Historical Significance
Ancient Romans believed moonstone was formed from frozen rays of the moon, while in India, it is considered a sacred 'dream stone'. It was a favorite of the great designer RenƩ Lalique and other 19th-century Art Nouveau jewelers. Today, it remains one of the most popular gemstones for those who appreciate natural phenomena and delicate beauty. It is a birthstone for June, along with pearl and alexandrite.
Adularescence & Varieties
The magical sheen of moonstone is called "adularescence." It occurs when light scatters between microscopic layers of feldspar. The finest classical moonstones are transparent with a blue sheen. The popular "Rainbow Moonstone" is technically a variety of Labradorite (plagioclase feldspar) but is accepted in the trade as a moonstone type due to its similar appearance and mystique.
Colors & Varieties
Colorless, white, gray, peach, blue (with adularescence)
Key Properties
- Adularescence (billowy glow)
- Feldspar group mineral
- Perfect cleavage
- Pearly/vitreous luster
- Exsolution layers
- Strongly associated with the moon
Uses & Applications
- Fine jewelry and cabochons
- Beads and amulets
- Ornamental objects
- Collector specimens
- Meditation and healing stones
Where to Find
- Sri Lanka - finest blue sheen
- India
- Myanmar
- Madagascar
- Brazil
- United States (Virginia, Pennsylvania)
- Tanzania
Frequently Asked Questions
Is Moonstone durable enough for an engagement ring?
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Moonstone is relatively soft (6-6.5) and has perfect cleavage, meaning it can split if hit hard. While beautiful, it is not recommended for a daily-wear engagement ring unless the wearer is very careful. A protective bezel setting is highly recommended.
How can I tell if my moonstone is real?
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Real moonstone has a moving, floating sheen that changes with the angle of light. Fake moonstone (often "opalite" glass) has a static, milky glow that looks the same from all angles and often contains bubbles. Real moonstone also feels cold to the touch compared to plastic or resin imitations.
What is the hardness of Moonstone?
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Moonstone has a hardness of 6 - 6.5 on the Mohs scale.
Where is Moonstone found?
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Moonstone is primarily found in Sri Lanka - finest blue sheen, India, Myanmar.
What color is Moonstone?
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Moonstone typically occurs in colorless, white, gray, peach, blue (with adularescence).