Moonstone – The Complete Guide
If you are looking to add a gemstone to your collection which will definitely turn heads, search no further than moonstone.
Moonstone is quite a remarkable stone, exhibiting a distinctive visual effect unlike any other. As you turn it in your hand, an ethereal sheen skips across the surface. This sheen may even appear to glow, often with a ghostly blue hue.
The “glow” is an illusion, but the appearance of moonlight suspended within the surface of the stone is so convincing that ancient peoples actually believed that moonstone was a form of solidified moonlight.
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What is Moonstone?
Classifying moonstone is actually a bit complicated. Moonstone may be any of several different members of the feldspar group, most commonly orthoclase, oligoclase, or microcline.
To add to the complexity, there are a few other gemstones which exhibit similar visual effects to moonstone such as plagioclase (a variety of albite), antiperthite, and anorthoclase.
There seems to be a fair amount of controversy surrounding plagioclase and whether or not it should be classified as moonstone.
For the sake of simplicity as well as completeness, I will be discussing both plagioclase feldspars and orthoclase feldspars in this article, but I will focus mainly on orthoclase moonstones. Here are their chemical formulas:
- Plagioclase Feldspars: (Na,Ca)Al1-2Si3-2O8
- Orthoclase Feldspar: KAlSi3O8
I do recommend however that you check out this chart from the GIA:
That chart tells you how the GIA classifies moonstone, referring specifically to orthoclase feldspar.
Moonstone Properties and Color
Most commonly when you picture moonstone, you probably picture a white or colorless specimen which features a bluish sheen.
Moonstone actually comes in a wide variety of colors, however. Along with the white and colorless specimens, you can find moonstone which is blue, green, orange, pink, brown, purple, gray, or yellow. On the Mohs scale of hardness, moonstone is a 6, which positions it between apatite (5) and quartz (7).
The visual effect which gives moonstone its name is the result of the gem’s microstructure. Moonstone consists of a number of feldspar layers. This layering causes the light to diffract, resulting in the appearance of a mysterious “moonbeam” which floats across the gem as you turn it. This effect is known as “adularescence.”
Along with adularescence, moonstone may also exhibit a few other visual effects. One is a cat’s eye effect where a band of light appears to hover over the stone as you move it. The other is asterism. Asterism is the appearance of a “star” on the surface of the stone, such as you see with star sapphire. Asterism is not as common as adularescence and the cat’s eye effect.
Several varieties of moonstone have special names:
- Cat’s eye moonstone: These are of course the moonstone specimens which feature the cat’s eye effect.
- Star moonstone: These are the moonstones which feature asterism.
- Rainbow moonstone: Despite the name, this does not refer to a colorful piece of moonstone. It actually just refers to moonstone with a blue sheen. Just to complicate things, it may also refer to labradorite, which is a different feldspar gemstone and does typically exhibit a rainbow of hues. Go back and reference the GIA chart I shared earlier. This will help you to understand the difference between labradorite and true moonstone. Both are feldspars, but only moonstone is orthoclase.
Moonstone may be either translucent or transparent. The translucency can range widely; some stones are nearly opaque. The more transparent a specimen is, the higher its value will be—but it is very rare to find a really clear piece. Almost all moonstone will have a cloudy look.
While the color of the adularescence may vary, the bluish effect is the most highly valued.
Moonstone has no particular use in industry; it is prized for its aesthetic beauty. For that reason, its only common applications are in jewelry, sculpting and mineral collecting.
Feldspar in general does have plenty of functionality; because of its high alkali and alumina content, other forms are useful as fluxing agents, aiding in the production of ceramics, glass, paints, rubbers, plastics, and adhesives.
Moonstone Buying Guide
If you are looking to purchase moonstone, there are several factors you should pay close attention to:
- Color: While clear or white specimens with a blue sheen tend to be the most highly sought after, there are no rules here. Moonstone comes in almost every color imaginable, and you should pick a color which appeals to your or your recipient. Just keep in mind that the colors you are interested in will have an impact on the prices.
- Transparency: The more clarity a piece has, the more it will cost.
- Carat: Larger moonstone gems are more expensive than smaller gemstones which exhibit comparable quality in all other respects.
- Authenticity: Make sure that what you are getting is actually moonstone, and not some similar-looking gemstone like labradorite. Again, this gets to be a tricky area, since some gemstones which are classified as moonstone by some gemologists are not by others. Ultimately you should buy what you really want. If your heart is set on plagioclase, then get it—even if someone else doesn’t feel it should be classified as moonstone. Just know what you are getting!
Why didn’t I mention cut? Moonstones are sometimes faceted, but it is far more common to find them polished or even raw. Moonstone can be quite lovely in its raw form. Polishing does a better job at bringing out the adularescence than faceting.
Plus, faceting is usually performed on transparent gemstones in order to showcase their clarity. Even though some moonstones are relatively transparent, they still tend to be a bit too cloudy for this to work well.
You might think that moonstone would be expensive, but it is actually quite reasonably priced. You can get a strand of high quality moonstone beads wholesale for around $10. If you are shopping for larger pieces, the price can vary quite a bit from one specimen to the next, but you can expect to pay anywhere from $1-$10 for 3-5 carats.
The more transparent a specimen is and the more pronounced the adularescence is, the more you will pay.
Because moonstone is relatively common and inexpensive, you will find it used in numerous jewelry creations. Larger pieces may be used to make pendants or brooches, while smaller pieces may be used in the creation of rings or earrings. Moonstone beads for necklaces and bracelets are also very popular.
Moonstone Engagement Rings
Moonstone is not a traditional choice for an engagement ring, but it is certainly an elegant one. While moonstone does not showcase the sparkle and clarity of diamond, it offers its own unique appeal. Because many moonstones are colorless, they can match anything.
Looking for something other than white? The rich variety of colors available provides you with an endless array of options.
- Because moonstone comes in every color, there is something for everyone. You can match moonstone to any band color, any skin tone, and any wardrobe.
- The adularescence of moonstone is very eye-catching. You can be sure that a moonstone engagement ring will make for a fabulous conversation piece.
- Even though moonstone is not traditional, accent diamonds can still be worked into the setting to add a bit of sparkle and shine back into the ring.
- Moonstone is only a 6 on the Mohs scale of hardness. Contrast that with the 10 that a diamond rates. Because diamonds are so hard, they are perfect for everyday wear. You are unlikely to scratch or break a diamond ring. A moonstone ring on the other hand may scratch or fracture easily, so it is not as suitable for wearing each day. On the bright side, if it does break, replacing it may be a lot less expensive.
- Moonstone is not traditional. Many recipients will only be happy if they are wearing a diamond ring to celebrate their engagement.
- Moonstone is not in itself an investment. In some ways, that is a good thing. The more money you save on the stone, the more you can spend on the band or on the wedding itself. But it is a detractor in the sense that the stone itself does not make for a valuable heirloom. Then again, if you spend enough on the setting, the ring itself may still be very valuable.
How to Clean and Store Moonstone
- Cleaning Moonstone: Not only is moonstone only a 6 on the Mohs scale, but it also has two cleavage directions. These both make it extra prone to breakage. That is one of the reasons why moonstone rings are not as common as moonstone pendants and earrings. It is also why you need to be extra careful cleaning it. Never use ultrasonic or steam cleaners. Always use warm water with a mild detergent. Hand wash or scrub the stone with a soft toothbrush. Rinse thoroughly so no soapy residue remains. Air-dry it or mop it gently with a soft cloth.
- Storing Moonstone: Keep moonstone away from high light or heat, as both can cause it to fracture. Store it in a cool, dark place, preferably in a pouch or box that separates it from the rest of your jewelry. This will prevent it from coming into contact with harder gemstones or metals which might scratch it.
- Wearing Moonstone: Moonstone can be damaged not only by light and heat, but also by hydrofluoric acid. That isn’t something you’ll have in your bathroom cabinet, but it is an indication of moonstone’s instability when exposed to harsh chemicals. So keep moonstone away from common household chemicals—detergents, cosmetics, and the like. Wear it with care, and be sure to take it off before you do anything active. Never wear a moonstone ring when you are doing work with your hands.
As moonstone is such a distinctive gemstone, it has quite a rich history. It is easy for historians and archaeologists to trace its use back to ancient times. Many cultures around the world prized moonstone and believed that it possessed mystical qualities. Ancient Romans, Greeks, and Indians believed that moonstone was quite literally composed of solidified moonbeams.
For this reason, moonstone was closely associated with the lunar gods of the ancient Greeks and Romans. Many believed that it was a lucky stone to carry.
You may sometimes hear moonstone referred to as “adularia.” In fact, you might even hear some people say that adularia is one type of moonstone.
Adularia is not a specific type of moonstone—it is simply another name for it. One of the first mines of high-quality moonstone was found in the Swiss city Mt. Adular, now called St. Gotthard. Just as the city is no longer known as Mt. Adular, moonstone is no longer commonly referred to as adularia.
Moonstone rose to new prominence during the Art Nouveau period. Famous designers like René Lalique and Louis Comfort Tiffany took a fancy to moonstone and incorporated it into a number of famous custom jewelry pieces.
In the 1960s, moonstone became popular once again. That was the age of the hippie movement, and moonstone had just the right ethereal, whimsical quality to capture the spirit of the movement.
Since then, moonstone has remained a trendy gem, though its popularity has arguably been eclipsed in recent years by labradorite.
Moonstone’s associations are the obvious ones—it is linked to the moon, femininity, and fertility. It is connected to change, cycles, and renewal.
It is also the state gemstone of Florida. This is somewhat unusual, as most states choose gemstones which are actually mined from their land. Moonstone doesn’t occur anywhere in Florida. But because the moon landing flights were launched from the Kennedy Space Center, the stone has been selected in order to commemorate them.
A nice introduction to moonstone that shows some great examples of ‘regular’ moonstone and rainbow moonstone.
Even though moonstone has quite a distinctive look to it, there are a number of gemstones which are similar, related, or may be easily confused with it. Here are some to be on the lookout for:
- Labradorite. This is a plagioclase feldspar mineral which can be found in igneous rocks. As discussed previously, it is often referred to as “rainbow moonstone,” but it is not technically a type of moonstone because it is not orthoclase. Of course, some people still like to classify certain plagioclase feldspar minerals as moonstone, so this is an argument you can have with a gemologist. Labradorite exhibits a slightly different visual effect known as “labradorescence.” While labradorite does tend to exhibit blue as a principle hue, pieces often contain a rainbow of hues.
- Peristerite. This is yet another plagioclase feldspar mineral, a form of albite. Like labradorite, it is usually found in igneous rocks. Typically peristerite is white or whitish with a blue iridescent sheen. Sometimes it exhibits adularescence. Like labradorite, it is sometimes classified as a form of moonstone, but many gemologists contest that classification.
- Larvikite. Larvikite isn’t actually a mineral; it is a type of igneous rock. As you might guess, this dark grey rock contains feldspar crystals, typically thumbnail-sized and numerous in quantity. Because there are alternating layers of plagioclase and alkali feldspar, it has a silvery bluish sheen. It is not a true form of moonstone, but it is often referred to as “black moonstone.”
- Carnelian. Carnelian isn’t actually all that easy to mix up with moonstone, but it is worth a quick mention. Carnelian may bear a resemblance at a glance to reddish, peach, and brownish moonstone specimens. Unlike moonstone, carnelian exhibits no special visual effects. The lack of adularescence makes it easy to tell the two gems apart.
- Antiperthite. This refers to a piece of feldspar which consists mostly of plagioclase with K-feldspar inclusions. While this gemstone doesn’t typically look like moonstone, there is no common generic name for it. For this reason, it may be grouped with moonstone.
- Anorthoclase. This stone is classified as a “high-temperature solid solution series.” It can be found in volcanic rocks, and may showcase the same blue sheen as moonstone. It has no common name, and thus may be referred to as moonstone.
Few gemstones have the mysterious charm of moonstone. The bluish sheen which floats across its surface gives it an almost magical allure as if it has its own internal light. Even though we now know that moonstone isn’t made out of solidified moonbeams, it still looks as if it is.
Moonstone makes a beautiful addition to any gemstone collection, and can make a wonderful jewelry gift for yourself or someone special!