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What Is Moonstone And How Is It Formed? Here Is the Answer

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If you’ve ever wondered how a moonstone seems to glow, whether or not it’s even natural, or what else is interesting about it, chances are the answer to all your questions lies in the profound process in which it forms.

Moonstone, a captivating gem shrouded in mystery and lore, has been the subject of countless wild tales and legends. Ironically, this enchanting stone comprises some of Earth’s most abundant mineral ingredients. Its mesmerizing beauty and widespread popularity have given rise to several look-alikes, both natural and synthetic, making it challenging to distinguish a genuine moonstone from its imitators at first glance.

However, its geological properties set it apart from these stones, and one must only perform some simple tests to be sure.

What is a Moonstone and How is it Formed
What is a Moonstone, and How is it Formed?

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What is Moonstone?

The beauty of moonstones has been adored in ancient Hindu mythology, through Greek and Roman culture, to the Art Nouveau period of modern history.

Modern geological science has uncovered the mysteries behind its appearance, which stumped so many cultures before – boiling it down to a complex formation process undergone by common minerals.

Moonstone is a variety of the feldspar group minerals orthoclase and albite.  During the moonstone formation, orthoclase and albite change each other, creating thin layers. When light falls between these layers, it scatters in many directions, producing a moonlike sheen, which is the adularescence phenomenon.

Not having the scientific resources and methods that exist today, all major mythologies in which it makes an appearance associated the moonstone with lunar powers because of its typical light feminine colors and soft glow.

The Romans thought that it was made of frozen moonlight. The stone was used in connection with the deity Luna and could be found at many of her places of worship.

Moonstone’s Hindu lore speaks of the stone being embedded in the forehead of the Hindu moon god Ganesh.

During the Art Nouveau period, moonstone was used in intricate jewelry that sported curves and flamboyance, which was typical of the time. The stone itself was cut in smooth curves.

Moonstone is a type of feldspar, which, as a whole, accounts for 60% of the minerals on the crust of the earth. Its chemical formula is KAlSi3O8.

It can display several different colors: typical varieties are colorless, white, beige, or silvery blue, but it has been known to commonly show up in green, darker brown, or reddish-brown as well.

It displays perfect cleavage, which can cause it to be very fragile even with a Mohs hardness of 6-6.5. Perfect cleavage means that the stone breaks along flat planes that can reflect the light easily because of the absence of imperfections.

The key attribute of a moonstone is its adularescence. In finer moonstone specimens, the mineral’s adularescence forms a distinct gleam from the center of the piece.

This gleam can sometimes expose the internal structure of the stone, which consists of a multitude of minuscule layers which, if well-defined, will take the form of a square lattice inside the piece. Lower-quality moonstones exhibit a shimmer or very little adularescence, especially if unpolished.

TIP: Putting a value on a moonstone differs from many other colored gems. Find out more about how valuable moonstone is in the article below:
Are Moonstones Valuable Rocks? The Real Worth of Moonstones

How is a Moonstone Formed?

The internal structure of moonstone, which is responsible for many of its unique properties, comes directly from the amazing process that forms it.

Such a unique process results from the slightly different chemical properties of the specific feldspar varieties that form it.

Moonstone didn’t come from the Moon. It is formed on the Earth during magma cooling. Orthoclase and albite gradually solidify from the magma intergrowing with each other. As a result, the minerals create stacked, alternating layers that are responsible for the moonlight sheen we observe on the gemstone.

The two varieties of feldspar which make up moonstone are orthoclase and albite. The slow rate of their cooling allows the first constituent to harden well before the second.

As it hardens, the material, which is still liquid, tends to stick together, but while the two feldspar types have such similar densities, the liquid cannot travel very far.

The microscopic layers form from the first ingredient solidifying into a lattice while fighting for space with the liquid ingredient.

The liquid layers then start to solidify. Without any foreign disturbance, the gemstone structure is determined at this point and needs only to harden before it becomes a gemstone.

If other minerals are present during this process, it is easy to see how the fragile system could be disrupted, either by a liquid persisting after everything else solidifies or a solid forming too early, breaking the lattice, and a lesser quality stone produced as a result.

Similarly, with a cooling process that is too quick, both ingredients solidify at similar times and don’t have time to form the exact crystal structure.

TIP: Moonstone is a popular type of stone to use for rock tumbling. Check out the step-by-step guide on how to tumble moonstone in the article below:
Can You Tumble Moonstone? Try These 4 Simple Steps

How to Tell if Moonstone Is Real?

It is true that the moonstone has been revered throughout human history, but it’s also valuable today as a gemstone. Like anything valuable, people have found a way to reproduce it with disturbing accuracy.

If you’ve found a gemstone in a rock or jewelry shop and wonder if it is real, this section can help you. If you’ve found a stone in the natural world and think it might be a moonstone, the identifying process section is for you.

Opalite, labradorite calcedony, and many cloudy/milky-colored stones, especially if they are of higher quality, can sometimes mimic some properties of moonstone, even though they have a chemical composition far from it. Adularescence is a good giveaway that you’re looking at a moonstone, but if it looks too shiny to be true, it may be labradorite, aka rainbow moonstone.

If the gleam shows bright colors but seems to be coming from the stone’s surface, it may be an opal. It may be calcedony if it seems duller or less refractive than many pictures you’ve seen of moonstone.

Opalite is also often confused with moonstone because it displays a shimmer that can be typical of adularescence. However, this is a glass that is man-made to mimic the qualities of moonstone. If you’re in a store, this could also be sold as opalite moonstone, opalite quartz, or sea quartz.

Labradorite is also sometimes confused with moonstone because of its color. In fact, a variety of labradorite is called rainbow moonstone.

The difference between this stone and real moonstones is that this stone is nearly perfectly clear, while even the clearest moonstones will have a more cloudy color.

TIP: The problem with fake rocks has been quite common in recent years. Find out how to know the difference between real and fake moonstones in the article below:
Real vs. Fake Moonstone: Focus on These 8 Differences

How to Identify Moonstone?

How to Identify Moonstone?
How to Identify Moonstone?

Geologists typically field-verify the identity of a stone by leveraging its known properties, such as hardness and cleavage, and performing tests to match the performance of the sample to how they know a sample of a certain mineral would act.

The best way to immediately recognize a moonstone is from its adularescence. It can look different depending on the sample. Hold the stone in light, examine it for translucent or semi-transparent areas, and try to deduce whether or not it reflects or emits light differently than you’d expect.

If you have a raw sample, it should still show small signs of this property, but washing the stone is a good place to start.

If unsure, chisel off a small impurity in the sample or simply chip off a small piece and see if the exposed area displays these symptoms. You must resort to more complicated tests if you cannot identify adularescence in your prospective moonstone.

Before you get out your hardness testing kit, let’s sit back a second and examine that glint you’re catching but don’t want to jump right in and characterize it as adularescence.

One way it can appear is so distinguishing that the effect has been named “cat’s eye.” Many stones reflect light well, but the structure of the moonstone causes the light to not only reflect directly but also permeate deeper inside the stone, sometimes visible as faint lines crossing in a geometric “X” behind the main reflection.

Another way that adularescence can present itself in moonstone is under the surface. The scattering of light through the stone will sometimes cause different colors to appear outside of the reflection area.

Hold your stone in the light and turn it around slowly, looking for light or colors that don’t follow the same path as the reflection.

If you don’t see any of these telltale signs, your moonstone may be too dirty or just shaped in such a way as to inhibit this glowing property. If so, test it for hardness.

Typically, stones with similar properties to moonstones, such as opal, chalcedony, or labradorite, are much harder or softer than moonstones’ 6-6.5 rating.

BTW: Do you want to know more about rock and mineral identification? The books listed below are the best ones you can find on the internet (Amazon links):

Does Moonstone Come from the Moon?

All the remembered theories for the moonstone’s unequaled qualities, which were developed before modern science, have something to do with the moon.

While we know that moonstone is formed from feldspar, one of the most abundant substances on earth, it does not come from the moon. Feldspar is also found abundantly on the moon’s crust, but potassium feldspar is very rare, and therefore, it is quite improbable that any moonstones exist on the moon.

To crush the myths and lore created by all these fabled civilizations about moonstones with what seems like basic science seems a bit of a shame. However, I see it as a testament to the geological wonders that this world can actually create.

Something with the beauty that demanded an ethereal explanation from some of the most pioneering civilizations happens naturally through physical processes right here on Earth. Oh, the wonders of gemstones!

TIP: So the moonstone does not come from the moon, unfortunately. But don’t be sad; some rocks come from the moon. The real Moon rocks. Read more about them here:
Moon Rocks: Everything You Need to Know About Them

Where Does Moonstone Come From?

The name moonstone is kind of misleading as it evokes thoughts that moonstone could probably be brought from the Moon. Moonstone is called so because of its moonlight-like appearance. Nothing more. 

The moonstone comes from the Earth. It was formed here as any other gemstone or rock due to magma solidification. Moonstone is a trading name for a common potassium feldspar mineral with a moonlight-resembling sheen on its surface. The Earth is the moonstone’s birthplace without any objections.

What is the Moonstone Made Of? 

Now we know that moonstone is a variety of very common orthoclase minerals. To clarify, let’s find out what the moon is made of and see that there is nothing similar in mineral compositions.

The Moon crust is mostly composed of plagioclase feldspar (anorthosite).  Minerals like pyroxene and olivine are typically seen in the lunar mantle. Lunar rocks are largely made of the same rock-forming minerals found on Earth. The dark spots on the Moon (lunar maria) are composed of basalt.

Do Moonstones Glow in the Dark?

Moonstone sometimes displays the light neon green, blue, and pink hues that characterize phosphorescent materials.

They also emit light from unnatural positions, sometimes far away from the point of reflection. This could make some believe that moonstones are phosphorescent.

However, moonstones are not phosphorescent materials and do not glow in the dark. Such materials are unique because they emit stored energy through light. While moonstones store energy just like all materials, this energy is given off, as is typical, in the form of heat.

All myths that moonstones glow in the dark come from the astonishing property of adularescence, which makes complex reflection patterns seem like the light emits them.

If no light currently shines on a moonstone, it will not display its adularescence. However, just because they don’t “glow” in the dark doesn’t mean they cannot produce some interesting effects when combined with the right light/dark placement.

If you’re looking for a glow-in-the-dark effect, direct a small amount of light at a moonstone with a dark background, and if it is positioned correctly, its adularescence may seem to glow in the dark.

TIP: Do you know what rocks and minerals glow under black or UV light? Check them out in the article below:
12 Rocks & Minerals That Glow Under UV Light & Black Light

Is Moonstone a Natural Stone?

We’ve already learned some other natural and manmade stones that approximate moonstones and some ways to ensure the specimen you are looking at is actually a moonstone.

Real moonstones are completely natural stones that form when two specific feldspar minerals solidify slowly from magma into stone, giving them time to separate because of different melting temperatures and form minuscule layers, which reflect light between them in a complicated way to form the phenomenal sheen that is exhibited by moonstones. 

Opalite is an unnatural stone that is made to look like moonstone. Opalite is glass that is made from small spheres of SiO2 (silicon dioxide), which are stacked in a geometric pattern.

High temperatures melt the mixture into the glass. It sometimes contains air bubbles resulting from impurities in this process. It can look blue or milky white, depending on the background. However, it is completely separate from the moonstone.

Is Moonstone Man-Made?

Moonstone is a natural mineral that has a natural optical phenomenon perceived from our side as a moonlight sheen. The mineral is absolutely natural, and it’s not man-made. There are some man-made imitations of moonstones. They are artificial glasses that imitate the appearance of natural stone.

Synthetic man-made ones imitate the same as natural diamonds; there are some moonstone substituents.

As described in the previous chapter, the most common man-made imitation of natural moonstone is opalite. Sometimes, gemologists report man-made iridescent coating on quartz, which imitates moonstones.

Nature has a rich fantasy of creating gemstones that are hard to believe to be real. Real natural moonstones are truly beautiful. Please consult with experts to avoid any man-made fakes and imitations and to hook the best-quality natural moonstone into your collection.

Is Moonstone a Precious Stone?

There are many different ways a moonstone can present itself, and while all of them are moonstones, some are considered to be of a different quality than others.

Moonstone is a precious stone. Sometimes, the best-quality stones cost up to $300 per carat. The most precious moonstones are perfectly clean and have distinct and evenly distributed adularescence. Moonstone is a desirable gemstone for high jewelry manufacturing.

If you want to find a moonstone and trust me, there is nothing more exhilarating than finding a gemstone in its natural form, and you’re in luck because they are found worldwide.

The next article in this series will tell you where to look. If you want to know the value of a moonstone or how to find out the value of a specific moonstone specimen, the last article in this series will tell you all you need to know.

TIP: Do you want to know how and where to find moonstones worldwide and in the USA? Check out the ultimate guide in the article below:
How and Where to Find Moonstone? The Ultimate Guide