Star Sapphire Buying Guide: Prized Inclusions and Asterisms

Last Updated on March 14, 2023 by Juli "Jewels" Church

Curious on how to buy star sapphire gemstones? Wondering how they happen to begin with? 

If so, you're in the right place. In this Learning Guide, I'll answer these questions and more about buying star sapphires:

  • How to tell if you have real star sapphire
  • How to pick out star sapphires 
  • How much do star sapphires cost?

What is a Star Sapphire?

If someone is advertising a star sapphire, the average jewelry buyer would probably assume they were being sold a fake. That's because star sapphires look a lot different from your typical faceted blue sapphires.

Star of Asia Star Sapphire at the Smithsonian Museum  (credit: Tim Evanson

Star sapphire is a real sapphire, formed from the mineral corundum. But star sapphires are cut in a much different way than faceted sapphire engagement rings. Instead of faceting angles, the rough sapphire is cut in a rounded fashion, called a cabochon shape.

Many gemstones can be cut en cabochon, but only certain stones are capable of becoming "star" stones. Star sapphire gets its name from the six rayed star that appears in some sapphire cabochons.

Star sapphire exhibits an optical phenomenon called asterism. Just as faceted sapphires have internal inclusions, so do star sapphires. The mineral rutile produces silk inclusions in the stones, which can result in the star effect when cut into cabochons.

Rutile inclusion in clear quartz (credit: Robert M. Lavinsky)

Asterism vs Chatoyancy in Gemstones

Asterism is often linked to another gem phenomena called chatoyancy. You might know chatoyancy as the cat's eye effect. Instead of casting a star shape when cut into cabochons, a glowing sheen is produced by the rutile silk inclusions in the gemstone. The rutile silk resembles the eye of cat, hence the name.

Asterism in Pink Sapphire and Blue Sapphire. Chatoyancy in Yellow Sapphire (credit: greyloch)

Asterism is the star effect and the stars can have a different number of rays. Typically, a 6 rayed star sapphire is the goal. However, star stones can have more than 6 rays. In rare occasions, there have been 12 rayed star stones!

Star Sapphires vs Star Rubies

When most people think of sapphire engagement rings, they picture a blue sapphire center stone. Blue sapphires are also commonly known as the September birthstone. But the truth is, sapphires come in a rainbow of colors, including colorless.

Sapphire colors besides blue sapphire and white sapphire are called fancy sapphires. This is similar to how colored diamonds are often called fancy color diamonds. Other colored sapphires can have the star effect, but the most common are blue sapphires, pink sapphires, purple sapphires, and black star sapphire. Yellow sapphire with asterism also exist, but it's harder to see the rayed star in its reflection.

colors of sapphire

The only color that sapphires don't come in is the color red. That's because red corundum goes by a different name: ruby. So, instead of a red star sapphire, they are called star rubies.

Star Ruby credited IslesPunkFan

Where are Star Sapphires Found?

Fine star sapphire can be found in various corundum deposits around the world. Many countries are capable of producing rutile inclusions . Some of these places include (but not limited to):

  • Sri Lanka
  • Myanmar (Burma)
  • Thailand
  • Brazil
  • Australia
  • Madagascar

How to Pick a Star Sapphire

Whether you're in the market for a purplish hue star sapphire or a rich blue color star sapphire engagement ring, there are some things you should keep in mind. Here are my best tips for picking out a star sapphire:


I've mentioned this before. If the person selling the star sapphire you want has it for a high price, you'll want to make sure everything they're saying about the stone is are legit.

Gemstone grading reports are your key to knowing the grades, origin, and treatments of your star sapphire. But anyone can create a fake gemstone report, so make sure the certifying lab is recognized in the jewelry industry.


This one is pretty self explanatory. Observe the domed cabochon to make sure there aren't any irregularities in the shape. Look for chips, dents, or cracks throughout the stone. If you're buying online, make sure you can see HD images or 360˚ video.


Obviously you want a star sapphire with needle like inclusions to produce a well defined star. But other inclusions can also be found in corundum. Dark mineral inclusions can create black spots on the cabochon, which brings down the value. In turn, these are less expensive.

Light Performance

The downside about not seeing your star sapphire in 360˚ video or in person is that pictures can be misleading. You might think you're thumbing through a catalog of blue sapphires with prominent star effects, only to find out the star blue sapphire looks much different in person under a bright light.

The star effect is best seen under a bright light when the stone is angled left to right. By observing the light performance of the star stone, you can see how prominent the star is as well as the way it has more of a glowy effect rather than a solid look like in pictures.

Carat Weight

If you really want the unique look of a star sapphire, you'll need to get one in a higher carat weight. Though cheaper, star stones under 1 carat make it difficult to see the star effect in the stone.

But on the flipside, cabochon cut gems already stick out no matter what setting they're in. So, if you go up in carat weight, a star sapphire engagement ring would be more vulnerable to damage.

How Much Does a Star Sapphire Cost?

Different colors of sapphire can display asterism, but blue sapphires with the star effect are considered the best. Black star sapphire also commands some value, even more than a faceted black sapphire.

Black Star Sapphire credited Factor801

Star sapphire with larger carat weights command higher prices. In lowe carat weights like between .5-1 carat, they are very affordable.

But the best star sapphires between 1-5 carats can go up to $1,200 per carat. Yellow sapphires and other sapphire colors usually go up $500 per carat in this size range. Finally, black star sapphire of this size go for a frugal amount of $30 per carat.

Where to Buy Star Sapphires?

Buying star sapphires is difficult because they're not regularly sold at the same retailers that offer diamonds and engagement rings. You're likely going to find individual sellers or local jewelers that either have the stones or can source them for you.

A well known online jeweler that has a bunch different natural star sapphire stones is the Natural Sapphire Company. They also offer video to show you exactly how their stones appear in the light.

How to Tell if Star Sapphires are Real

There's a big cost difference between fine star sapphires cut from natural sapphire and star sapphires from synthetic sapphires. Therein lies the problem when determining if you've got a real star sapphire on your hands.

High quality star sapphire jewelry can be pricey, so you want to know that you're getting the real thing when spending the money. That's why it's important to make sure that you read all the details about the star sapphire and the company you may be potentially buying from.

It's harder to find a legitimate retailer online when looking for natural sapphires with asterism. That's because most fine jewelry retailers offer their customers a faceted sapphire ring.

A buyer wouldn't be able to tell the difference between a synthetic star sapphire and a natural star sapphire. They have all the same quality and physical attributes, but the star is created in the gem.

Star blue sapphires with an intense blue color and a perfect six distinct star are likely to be fake. Some star sapphire fakes have been glass filled, which can also produce fake rubies and sapphires of the faceted cutting style too.

Star sapphires can be a pretty penny, depending on the sapphire's color, carat weight, and how how

Treated Star Sapphires

A star sapphire ring can be treated, but still be a real sapphire ring. People get thrown off with words like synthetic, lab created, natural, and treated. I don't blame them. It took me a while to get my head to wrap around it. The jewelry industry is trying to phase out certain words to use lab created instead of synthetic, but you'll still find the terminology all over the industry.

Both star sapphire and faceted sapphire often receive heat treatment in order to bring light toned gems to a medium tone or to enhance clarity. Sometimes both. Heat treatment and other gemstone treatments may be recognized as standard and don't have a huge effect on price value.

But there are some gemstones and certain treatments that will improve the quality of gemstones, but aren't permanent. Such gems with these treatments often bring value and price. Oftentimes, the treatments will have to be re-applied at cost.

The best way to determine if you have untreated stones is by only buying star sapphires that come with grading reports or certificates. A grading report is a document that tells you all the specifics of your star sapphire including whether or not they're natural stones. They will tell you the different hues, clarity, and divulge any treatment.

Treated star sapphire is virtually impossible to tell from an untreated star sapphire. Only the most knowledgeable gem experts on sapphire jewelry would be able to tell.

Do Star Sapphires Make Good Engagement Rings?

Typically faceted sapphires make an excellent engagement ring. It's the most durable of all colored gemstones. Star sapphires have the same durability, but they're more vulnerable. Because of the rounded shape of a cabochon cut gem, they can still get scratched after years and years of wear.

The other thing you want to think about is the size of your stone. The best star sapphires are presented in larger carat weights and not everyone wants a big stone on their engagement ring.

Cabochons are a bit bulky already, so when you increase the carat weight, it's even bigger. Some might find it too heavy or too "loud" for their taste.


Star sapphires are a result of a gemstone phenomena called asterism. Other gemstones are also capable of asterism, but star sapphire tends to be the most popular. The blue sapphire, that is.

Though blue sapphires are the color sapphire sought out for star gems, other sapphire colors exhibit asterism too. Star sapphire may be heat treated for color or clarity, created in laboratory, or even be glass-filled as a star sapphire imitation. The best way to ensure you've got a real star sapphire is by choosing one that is certified.

There are many elements to picking out a high quality star sapphire. The biggest ones have to do with the clarity of the star, the light performance, and the carat weight. The rayed star should be centered and have individual points with no blotches to detract from.

Star sapphires can be very rare and valuable in large carat sizes with prominent stars. While I don't advise wearing them for engagement rings, they can make very beautiful cocktail rings, pendants, or earrings.

Star sapphire is one of the many phenomena gemstones. It is a unique design and stone preference who wants something outside the box.

I hope you've enjoyed everything there is to learn about star sapphire and feel much better equipped when picking one out on your own!

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