Astrophyllite vs. Arfvedsonite – The Similarities and Differences (With Photos)

By Dr. Keith Jackson - Geology PhD

| Updated

Astrophyllite vs. Arfvedsonite – The Similarities and Differences (With Photos)

By Dr. Keith Jackson - Geology PhD

Updated

Minerals like astrophyllite and arfvedsonite are very interesting to rock fans and scientists. They are different from each other in many ways that make them special in the world of minerals.

Both have unique physical traits and can be found in different parts of the world. Their appearance and where they are from are the main things that make them different.

These materials are like distant cousins in the big family of rocks and minerals. Each has its own story to tell.

We explore the fascinating worlds of astrophyllite and arfvedsonite in our article, looking at how these two minerals are alike and different in different ways.

From how they look to how they were formed, we’ll look at each feature in detail to show the minor and not-so-subtle ways these two minerals are different and how they are the same.

This will give you an exciting overview of these two excellent minerals and how they fit into the bigger picture of geology.

The Major Differences

They both look beautiful, but astrophyllite and arfvedsonite are very different in important ways that will help you tell them apart. These things make them stand out:

Appearance – Arfvedsonite have prismatic crystals

A distinct rough and natural arfvedsonite mineral
Arfvedsonite photo provided by and available for purchase at YEMCrystals

Astrophyllite and arfvedsonite are both silicate minerals, but they look very different from one another, which will interest anyone who likes minerals. The unique and interesting structure of astrophyllite is well known.

It usually gathers in bladed, radiating, stellate aggregates that make a pattern that looks like a starburst. This pattern is easiest to see when it is set in a contrasting matrix.

This structure gives the mineral a three-dimensional look that you don’t see very often in other crystals. Its sub-metallic sheen makes it even more appealing, and fans are always on the lookout for it.

Arfvedsonite, on the other hand, looks darker and less bright. What makes it unique is that it forms long, segmented crystals.

Astrophyllite has crystals that are shaped like starbursts, but Arfvedsonite’s crystals are more straight and long, and they often form groups that are parallel or radial.

Arfvedsonite usually has a vitreous or glassy sheen, which, along with its dark color, can make it look a little sad when compared to Astrophyllite, which is bright and shiny.

Both minerals can be easily recognized because of their different looks, which shows how varied the world of minerals is.

Chemical Composition – Astrophyllite has titanium silicate

A rare and unique astrophyllite mineral
Astrophyllite photo provided by ARTelStones

Astrophyllite and Arfvedsonite are both complex silicate crystals, but their chemical makes-up is very different. The formula for astrophellites, (K,Na)₀(Fe++,Mn)₇Ti₂Si₈O₂₄(OH,F)₇, shows a special mix of elements.

In addition to potassium (K) and sodium (Na), it has a lot of iron (Fe) and manganese (Mn), as well as titanium (Ti) and silicon (Si). Having hydroxide (OH) and fluorine (F) in it’s also very important to its structure.

Its unique physical qualities, like color and shine, come from this composition. The mix of iron, manganese, and titanium in Astrophyllite is very interesting because it gives it its bronze to golden-yellow color and shiny shine.

On the other hand, arfvedsonite is made up of Na₃(Fe++,Mg)₄Fe+++Si₈O₂₂(OH,F)₂. There is a lot of sodium (Na), iron (Fe), magnesium (Mg), and silicon (Si) in this mixture. There are two forms of iron in Arfvedsonite: Fe++ and Fe+++.

This gives it a dark green to black color. One big difference between the two is that arfvedsonite has less titanium than astrophyllite. There are also hydroxide (OH) and fluorine (F) parts, but they are not as concentrated as they are in astrophyllite.

This difference in their chemical make-up changes more than just their color and look. It also changes their hardness and ability to split. These different chemical ratios show how diverse and complicated mineralogy is.

They show how even small changes in the elements that make up minerals can cause big differences in their properties.

Cleavage – Arfvedsonite has good cleavage

A beautiful raw arfvedsonite mineral with black spots
Arfvedsonite photo provided by abijouxparis

One important way to tell the difference between minerals like Astrophyllite and Arfvedsonite is by their cleavage, which is how they break along certain lines. Two-way perfect cleavage is what makes astrophyllite stand out.

The characteristic cleavage makes thin, flexible sheets that can be peeled apart because the material comprises layers. Astrophyllite has a perfect cleavage because of the way its crystals are structured.

This lets it break along clear lines, making smooth, flat surfaces. This feature can identify the mineral, and it also makes the mineral look nice, especially when the sheets catch light and show off their unique color and shine.

On the other hand, Arfvedsonite has good cleavage, though it’s not as good as in Astrophyllite. The cleavage in Arfvedsonite is more like that in amphibole minerals. It has two lines of cleavage that cross each other at angles of about 60 and 120 degrees.

Because of this, long pieces are formed instead of the thin sheets that are seen in Astrophyllite. Astrophyllite has smooth, expected cleavage planes, but Arfvedsonite’s cleavage planes are not as clear, so its breakage patterns are not as regular.

This difference in cleavage changes how the rocks look when they are broken and how they are worked with and studied, whether in the lapidary arts or for scientific reasons.

Color – Astrophyllite ranges from bronze to golden yellow

A mesmerizing astrophyllite specimen with different earthy hues
Astrophyllite photo provided by Fossilera

Looking closely, you can tell the difference between Astrophyllite and Arfvedsonite because of their very different colors. Astrophyllite is praised for having colors that are both unique and striking.

Its colors are usually bronze to golden-yellow, and it often has a glossy sheen that makes it look better. Its warm color range comes from the iron and titanium in it, making the mineral look shiny and appealing.

Astrophyllite can even show flashes of coppery or bronzy tones in some lights, which makes it look better. When the mineral is seen in slabs or thin parts, where the light can interact with its crystalline structure, these bright colors stand out even more.

Arfvedsonite, on the other hand, is known for having darker shades. It usually comes out in shades of dark green to almost black. Because it contains iron, it has a much darker and more muted color than Astrophyllite.

Instead of having the shiny sheen and warm colors of Astrophyllite, Arfvedsonite often looks like glass. Arfvedsonite’s dark, rich colors can make it less noticeable than Astrophyllite’s bright colors, but they also give it a unique and classy look.

The two rocks can be told apart at a glance because of their different colors, which also show how their chemical makes-up and crystal structures are different.

Density – Arfvedsonite is more dense

A perfect rectangular-shaped arfvedsonite slab with cool streaks of patterns
Arfvedsonite photo provided by TwoRavensCrystalsUK

Astrophyllite and Arfvedsonite have very different densities, which is a physical feature that has a big effect on how they are identified and handled. The density of astrophyllite is usually lower, between 3.2 and 3.4 grams per cubic centimeter.

Its unique chemical make-up and crystal structure explain its relatively smaller density. Astrophyllite contains elements like potassium and titanium, making it less dense than many other silicate rocks.

When you touch Astrophyllite samples, you can tell they have a lower density. They feel lighter than they look, which can be surprising because they usually look heavy.

On the other hand, Arfvedsonite is a little more dense, weighing between 3.3 and 3.5 grams per cubic centimeter. This rise in density is because it contains a lot of iron and magnesium.

Holding Arfvedsonite up to your hand feels thicker and heavier than Astrophyllite because of these heavier elements. Arfvedsonite’s density is a key part of identifying it; its weight makes it easy to tell apart from lighter rocks.

This difference in density not only helps you tell these two minerals apart, but it also shows how different silicate minerals are and how small changes in their chemical make-up can cause big changes in their physical traits.

Hardness – Astrophyllite is softer

A beautiful astrophyllite natural gemstone with a gold strip in the middle
Astrophyllite photo provided by GemsartstudioUS

One important way to tell the difference between Astrophyllite and Arfvedsonite is by their hardness, which is a measure of how well they resist scratching. On the Mohs scale, astrophyllite has a relatively low hardness, usually around 3.

At this level of hardness, Astrophyllite is easy to scratch with a copper coin or even your fingernail if you press hard enough. Astrophyllite is soft because it has a unique crystal lattice structure that doesn’t strongly fight being bent or twisted.

Because Astrophyllite isn’t very hard, it needs to be handled carefully so that it doesn’t get damaged, and it can’t be used in jewelry or other places where toughness is important.

While arfvedsonite is only about 5 to 6 on the Mohs scale, it’s much harder than most other minerals. Because it is harder, Arfvedsonite is less likely to scratch or wear away than Astrophyllite.

It’s easy to scratch glass, but a knife won’t be able to scratch it. Arfvedsonite is harder than other minerals because its crystal structure is denser and more stable, with stronger links between its atoms.

The different hardness of these minerals not only changes how they are used and treated, but it also makes them easy to tell apart.

In the outdoors, for example, a simple scratch test can help figure out if a rock is Astrophyllite, which is softer, or Arfvedsonite, which is harder.

Luster – Arfvedsonite has a vitreous luster

A gorgeous arfvedsonite sphere with a beautiful pattern
Arfvedsonite photo provided by FossilBucket

Astrophyllite and Arfvedsonite have very different lusters, which are how their surfaces reflect light. This is one of the reasons why they look so different. Astrophyllite is famous for having a beautiful, submetallic to pearly sheen.

Astrophyllite has a shimmering, almost glowing quality that you can see most on its cleavage faces because of this luster. The sub-metallic quality gives it a shine that looks like metal, and the pearly quality gives it a soft glow.

Because Astrophyllite has so many different types of luster, it is very appealing and is often bought to show. This material’s texture and color range, from golden yellow to bronze, make it look nice, especially when it is polished.

On the other hand, Arfvedsonite has a glassy, or glass-like, shine. This makes the mineral’s surface more reflective and shiny, like glass that has been cleaned.

The vitreous sheen of Arfvedsonite makes its dark green to black color stand out more, giving the mineral a shiny and classy look. Arfvedsonite doesn’t have a shiny sheen like Astrophyllite does.

Instead, it has the clarity and brightness of a glassy substance. One of the most noticeable differences between the two gemstones is their different sheens, which makes them easier to spot.

The shine of each gemstone not only changes how it looks, but it also tells you about its crystal structure and chemical make-up.

Magnetism – Astrophyllite is not magnetic

An elegant polish astrophyllite with red spots
Astrophyllite photo provided by EarthMineralsLTD

Astrophyllite and Arfvedsonite are very different in how magnetic they are because they contain different amounts of iron and other magnetic elements. The lack of magnetic qualities in astrophyllite is what makes it unique.

Even though Astrophyllite has iron, the form and amount of iron present don’t generate any visible magnetic response. Astrophyllite doesn’t reply or talk to magnets when things are everyday.

Although it’s not magnetic, this property can be beneficial in identifying it, especially when compared to other minerals of the same color or structure that might be magnetic.

Although not very strong, arfvedsonite can have some magnetic features. It’s magnetic because it has iron, especially iron in the Fe+ state.

Because Arfvedsonite has iron, it can react to strong magnets, which is not seen in Astrophyllite. Arfvedsonite’s magnetic strength can change based on the type and amount of iron it contains.

This magnetic feature of Arfvedsonite can help with mineral identification because it makes it easy to tell it apart from minerals that aren’t magnetic, such as Astrophyllite.

This property can be regularly found with a strong or sensitive magnet because Arfvedsonite is not very magnetic.

Price – Arfvedsonite is less expensive

A huge slab of arfvedsonite stone with a smooth surface
Arfvedsonite photo provided by laurelmoon

The prices of gemstones are affected by many things, such as how rare they are, how much people want them, and how nice they look. The price differences between Astrophyllite and Arfvedsonite show this.

Astrophyllite is usually more expensive than Arfvedsonite because it is a rarer material. Its unique look, with a bright golden-yellow to bronze color and a design that looks like a starburst, makes it more appealing to collectors and enthusiasts.

Astrophyllite is very expensive because it is hard to find and looks beautiful. High-quality pieces can fetch a higher price on the mineral market, especially those with the characteristic luster and crystal habit.

Astrophyllite is more expensive because many people want to use it to make jewelry and decorations.

Astrophyllite is rarer, while arfvedsonite is easier to find and costs less. Astrophyllite is more popular with fans than Arfvedsonite, even though both are liked for their dark green to black color and mirror-like shine.

Its lower price comes from the fact that it is easier to find and not as well known. It’s important to keep in mind, though, that the price of Arfvedsonite can change, and that pieces of higher quality or from rare places can fetch higher prices.

Overall, both minerals have their draw, but Astrophyllite usually costs more than Arfvedsonite because it is harder to find and has a unique look.

Streak – Astrophyllite has a yellowish-brown streak

An elegant astrophyllite mineral with a pretty surface patterns
Astrophyllite photo provided by CrystalGemstoneShop

A trait that sets Astrophyllite and Arfvedsonite apart is the streak of a mineral, which is the color of its powdered form. Astrophyllite has a line that is a completely different from its regular color.

The powdered Astrophyllite leaves a brownish-yellow line. Although, when it’s stable, it looks more metallic and golden-yellow to bronze.

A lighter line color happens when light moves across the finely powdered mineral, showing its true color without the interference of crystal structure and surface reflection.

This yellowish-brown streak is a trait of Astrophyllite that can help you identify it, especially when comparing it to other minerals that look like it.

In contrast, arfvedsonite has a line that matches its color better. Arfvedsonite’s line is usually gray to black, but it shows dark green to black colors when crystallized or hardened.

Since iron is most of the mineral, the material and its powdered form are the same color. While other minerals may have a similar shine or crystal shape, Arfvedsonite’s dark streak is a key trait that helps you tell it apart.

Different streak colors of Astrophyllite and Arfvedsonite make them easy to tell apart while showing how their chemical makeups differ.

The Similarities

Although astrophyllite and arfvedsonite are not the same, they are interestingly similar in some ways. Someone who only knows how these gems look might be surprised by these facts.

Conductivity – Both arfvedsonite and astrophyllite are poor conductors of electricity

A smooth and round arfvedsonite gemstone
Arfvedsonite photo provided by CrystalGemstoneShop

Even though Astrophyllite and Arfvedsonite have different chemical and physical features, they are electrically conductive. In general, neither mineral is a good carrier of electricity.

This is something that most silicate minerals have, and both Astrophyllite and Arfvedsonite are silicate minerals. Silicate minerals are mostly made up of silicon and oxygen that are bound together with different metals.

Their structure doesn’t allow electrons to move freely. They don’t carry electricity very well because they don’t have many free electrons.

Iron, titanium, and magnesium do not change the conductive qualities of Astrophyllite or Arfvedsonite very much when they are present.

These elements can change how well some minerals carry electricity. Still, Astrophyllite and Arfvedsonite don’t allow electricity to flow because of how their structures are arranged and bonded.

So, when electrical tests are done on both materials, they show high resistance, which proves that they are not good conductors.

Formation – Astrophyllite and arfvedsonite are formed in nepheline syenites

An elegant polished and tumbled astrophyllite gemstone with a reddish brown hue
Astrophyllite photo provided by YolkaMohh

While Astrophyllite and Arfvedsonite are different in many ways, they were formed in the same way during the same natural process. It’s common for both minerals to form in alkaline igneous rocks that are high in sodium and potassium and low in silica.

Astrophyllite and Arfvedsonite are two examples of unique and complex silicate crystals that can form in this type of geological setting.

Nepheline syenites, a type of intrusive volcanic rock, are often the place where they form. People know these rocks for having low amounts of silica and high amounts of alkali metals, which makes it easier for crystals to crystallize.

Cooling and solidifying of magma are parts of the creation process. Astrophyllite and Arfvedsonite crystallize at certain temperatures and pressures.

The alkaline environment and the amount of elements present, such as iron, magnesium, titanium, and others, are very important in identifying the mineral composition during this process.

Fluorescence – Arfvedsonite and astrophyllite do not exhibit fluorescence

A mesmerizing tumbled arfvedsonite gemstone that resembles a night sky full of stars
Arfvedsonite photo provided by AwakeningsStore

Even though Astrophyllite and Arfvedsonite are made of different minerals, they behave similarly regarding fluorescence. When minerals are subjected to ultraviolet (UV) light, they give off light.

This is called fluorescence. Astrophyllite and Arfvedsonite don’t usually glow under UV light, which is something that many silicate minerals do.

The lack of fluorescence in these rocks is due to the chemicals that make them up and the chemical bonds that hold them together.

Minerals often fluoresce because they have flaws or elements that can soak up UV light and send it back out at different wavelengths.

Though, the parts of Astrophyllite and Arfvedsonite that make them up, like iron, magnesium, titanium, and silicate substances, don’t help this process.

This means that when these minerals are exposed to UV light, they don’t glow or shine like other minerals.

Location – Astrophyllite and arfvedsonite are both found worldwide

An amazing tumbled astrophyllite specimen with a shiny surface and dark blue hue
Astrophyllite photo provided by TheHungryMushroom

Even though Astrophyllite and Arfvedsonite are different in many ways, they can both be found in some places, which is likely because of similar conditions during their formation.

It’s common for these two minerals to be found in alkaline igneous complexes, which are rock formations high in sodium and potassium and low in silica. This particular climate is good for the growth of both Astrophyllite and Arfvedsonite.

They both are found in places known for nepheline syenites, a type of intrusive igneous rock, which is a striking similarity between them.

The Kola Peninsula in Russia is a great place to find both minerals because it has a lot of rare minerals and complicated geology. In addition, both can be found in Greenland, which also has large amounts of alkaline volcanic rocks.

These shared locations are not coincidental but indicate the similar types of geological processes and environments that give rise to these minerals.

The presence of Astrophyllite and Arfvedsonite in these specific types of geological settings suggests a link in their formation history, where the conditions were just right for these unique minerals to crystallize.

This similarity in location is an important aspect in understanding the geological history and distribution of these minerals on the Earth’s surface.

Other than that, you can also search in these amazing rockhounding locations for more chances of finding both minerals. hat they say they are, showing that they share a trait even though they are very different.

The Easiest Ways To Tell Astrophyllite and Arfvedsonite Apart

Astrophyllite at the top and Arfvedsonite at the bottom

If you want to buy one, you should know the difference between astrophyllite and arfvedsonite. There are several ways to tell them apart.

Observe their colors

Astrophyllite has a unique color. It’s usually a kind of shiny bronze or golden yellow. If you think about the color of a shiny new penny, that’s what astrophyllite looks like. It’s got this neat metallic look to it that makes it stand out.

Arfvedsonite is usually a much darker color. It’s typically black or a very dark green. So, if you see a bright and golden mineral, it’s likely astrophyllite, but if it’s dark and more like the color of the night sky, then it’s probably arfvedsonite.

Look at their luster

Astrophyllite has a luster that is kind of sub-metallic, meaning it shines like a metal but not quite as brightly. It’s more like a glow.

Arfvedsonite, however, has what we call a vitreous luster. This means it shines like glass. So, if the mineral looks really shiny like a piece of glass, it’s more likely to be arfvedsonite.

Check the patterns

Astrophyllite often forms in these starburst patterns, like little stars or fireworks. They are really pretty and unique.

Arfvedsonite doesn’t do this. Instead, it forms in long, thin crystals that can look like dark needles.

About Dr. Keith Jackson - Geology PhD

Keith Jackson is an avid rockhound who is constantly exploring new sites to expand his collection. He has worked as a professional Geologist for over 20 years and holds a PhD in Geology from the University of Nebraska-Lincoln, a Masters Degree in Geology from the University of Nebraska-Lincoln, and a Bachelors Degree in Geology from the University of Connecticut.

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