Complete Guide to Star Sapphire

Written by: Benjamin Khordipour, Jewelry and Gemology Expert
February 27, 2023 – Posted in: Jewelry Blog

Star Sapphires are a unique variety of precious stone that showcases a mesmerizing star reflection when viewed under direct light. Over the last few decades, these valuable sapphires have become the gemstone of choice for all kinds of jewelry, including engagement rings. Here, we’ll thoroughly introduce star sapphires, their origin, hues, treatments, and price. 

What Is a Star Sapphire?

cabochon star sapphire held by tongs with infographic of meaning

A star sapphire is a kind of sapphire that shows an opaque six-rayed star when exposed to direct light. The unique optical phenomenon is known as asterism; the star is created by light refracting off of strands of rutile present in the gemstone. The mineral rutile is primarily composed of titanium dioxide, which is characteristically white (it was used in chewing gum coloring, for example). 

These inclusions make star sapphires not translucent, unlike other sapphires. The star moves slightly following the relative position of the light source.

For a more prominent star, these sapphires are always cut into a high dome cabochon shape (French: en cabochon), drawing attention to any jewelry piece in which the gemstone is set. 

However, this type of sapphire is used for more than just aesthetic purposes. Some of the ancient meanings these gemstones acquired related to protection from illness and evil.

Star sapphires are found in various colors besides the characteristic deep blue. They are in Australia, Myanmar (Burma), Thailand, Sri Lanka (Ceylon), Brazil, Cambodia, Madagascar, the United States, Tanzania, Vietnam, Kenya, China, Pakistan, Rwanda, Zimbabwe, and Malawi. 

How Quality Works in a Star Sapphire

infographic quality of a star sapphire with example of sapphire ring with flower motif

The main characteristic of the Star Sapphire is the star that seems to be trapped inside the stone. This provides a unique and stunning reflection. When determining the quality of the stones, gemologists pay close attention to several aspects of the gem. The first and most important for star sapphires is the reflection of the star.

The best star sapphires are those in which you can see the reflection right in the center of the stone. For this, you have to look at it from above. Another important parameter is that each star ray should have the same length. Last but not least is the visibility of each ray. They have to be bright and clear. Blurry rays will indicate the stone is not of the best quality.

Another valuable quality indicator is the clarity of the gemstone. This is a bit more complicated to determine, especially if you’re not a professional. The asterism effect that you see in star sapphires comes from the inclusion of mineral rutile, which naturally compromises the stone’s clarity. 

The best star sapphires contain enough rutile to reflect a well-defined star without impacting the rest of the stone. These star sapphires are rare or difficult to make and are the most expensive.

Cutting and Treatments

Model using loupe to examine a rare sapphire and diamond ring

Proper cutting is crucial in ensuring the desired definition and orientation of the star. Only a few professional cutters use en cabochon cutting on pure sapphires. They need to know how to strike the right balance between carats, stars, and color, which makes these pros all the more valuable, trustworthy, and expensive.

However, natural sapphires rarely have the exact ratio or rutile and clarity to be perfect star sapphires. To improve the gemstone’s standing on the market, the Union Carbide Corporation started producing man-made star sapphires through its Linde division. Even now, there is a vast market of artificial Linde star sapphires and similarly manufactured gemstones. 

Gemologists and expert jewelers are usually the only ones who can tell a natural and artificial stone apart. They pay close attention to the minute differences between real and artificial star sapphires, examining the quality of the star reflection and each ray pattern under a microscope. Nonexperts on the subject may only rely on the general aspect of the star to make an evaluation. Lab-made star sapphires tend to look painted on. This means the reflection of the star looks too perfect to be real.

Finally, there are special treatments that intensify the color of the stone or its transparency. What’s more, these treatments can artificially induce the star effect. Therefore the gemstones are heat-treated in temperatures between 1,012 F and 2,732 F. 

Important Note: The highest quality star sapphires are the ones that haven’t received heat treatment.

How Much Is a Star Sapphire Worth? 

Beautiful Star sapphire surrounded by diamonds in gold mounting signed

While sapphires are rare, and star sapphires even more so, they are not as prohibitively rare or expensive as diamonds. This makes them valuable as alternative jewelry centerpieces on a slightly lower budget. 

When selecting a star sapphire to purchase, it’s important to understand what increases a gemstone’s value. In the first place, the quality and visibility of the star are the main factors that determine the price of a star sapphire. A sharp and perfectly-defined star is very difficult to find, which will highly increase the price of such stones. 

Other price-determining factors are the color and clarity of the gemstone. In more recent trends, the more transparent the stone is, the more valuable it will be. The rarest kind of star sapphires has a transparent blue body and a vibrant star in them. This gemstone can fetch tens of thousands of dollars.

As for the shape of the star sapphires, as we mentioned, they are always cut en cabochon with a high dome, which is the only way you can truly appreciate the star in it. This means that you can’t rely on faceting to direct the price.

Like diamonds, sapphires are weighed in carats. The value per carat for gray or lavender star sapphires ranges between $50 and $1,500. For traditional colors like blue, the price per carat for rings may vary between $500 and $2,000, depending on translucency and star quality. Some high-quality star blue sapphires will start at $10,000 per carat.

The Largest Star Sapphire

large star sapphire in elaborate gold enamel mounting

The stone’s distinctive qualities will affect the cost. The largest blue sapphire in the world (the Star of Adam) measures 1,404 carats and was discovered in 2015. The price of the stone exceeds $300 million. Before the discovery of the Star of Adam, the largest star sapphire was a 733-carat black star sapphire known as the Black Star of Queensland. Compared to other star sapphires, this unique gemstone showcases a much bigger and brighter star set on a completely black background. In 1947, the stone was sold to Armenian-born jeweler Harry Kazanjianfor for $18,000. It was loaned to the Smithsonian Institution’s National Museum of Natural History in Washington, D.C. in 1969.

To sum up, weight is not the only factor determining the stone’s price. The sapphire’s color and the star’s visibility are also very important. Gems with more rutile in them will be more opaque and lose some color, but the star will be more intense and prominent. The best combination is a good balance between the color of the gemstone and the visibility of the star. 

How Are Star Sapphires Made?

Jeweler using machine to cut a sapphire into star sapphire

The rutile needles must be packed tightly in parallel for the asterism phenomenon to occur. The result is straight lines that seem to float on the surface of the stone, providing a unique and mesmerizing effect. There are always three groups of crystals that intersect at a 60-degree angle from each other and connect in the center. This forms the appearance of a six-ray star. 

Although six-ray star sapphires are less common than traditional sapphires, there is an even rarer stone. This one has a twelve-ray star on it. The phenomenon occurs when the stone contains two types of inclusions: rutile mineral and hematite platelets. Rutile inclusions produce a whitish star, while hematite produces a golden star. During the crystallization process, the two stars superimpose on each other, resulting in a twelve-ray star. 

Star sapphires typically come in black, pink, or blue colors, but we don’t fully understand why rutile is more likely to be present in these gems.

The Demand For Artificial Star Sapphires

While these gemstones are present in nature, their high demand has opened the doors for a new market of artificial stones. The first development of synthetic star sapphires occurred in 1947 in the United States by the Linde division.

The distinguishing characteristic of a Linde Star Sapphire is a large star with straight and even rays, which is unusual to find naturally. The star is visible even in low light and remains stationary in relation to a light source. A natural sapphire’s star, on the other hand, has thicker, slightly uneven rays and moves to follow the light. 

Artificial gems are made in a variety of colors and cannot be easily distinguished from a natural sapphire by the untrained eye. Linde artificial stars typically have a small letter “L” etched on the bottom of the stone. Nevertheless, you may also come across Lindes without the letter. Unless you have some gemology training, you’re unlikely to spot the differences. 

Gemologists can use microscopes to see the tiny cracks which are typical of the intersection of facets. Additionally, synthetic stars won’t have the typical sapphire zoning found in genuine corundum. As a result, the body color may be bright and abnormally even throughout the stone. But again, at first sight, artificial gemstones may look real.

Colored Star Sapphires

modern star sapphire ring set in shiny platinum

The presence of a star in a precious gemstone is a remarkable phenomenon that is not easy to encounter in the world. Only a small portion of the sapphires mined worldwide exhibit this visual phenomenon, making it exceedingly rare. This explains why their value can be so high. 

Sapphires score a nine on the 10-point Mohs scale, just below diamonds. This makes them perfectly suitable for daily wear and an excellent choice for a durable engagement ring. 

While there are rings with star sapphires in many different colors, some are more common than others. Here is a complete guide to the star sapphire colors.

Blue Star Sapphire

Star sapphires in royal blue displaying a sharp six-ray star are incredibly rare. This makes them an excellent choice for a one-of-a-kind engagement ring. These gemstones can come from mines in Australia, Madagascar, Sri Lanka, and Bruma. 

Due to the captivating reflection of a star enhancing their distinctive deep blue color, blue star sapphires are among the most sought-after gemstones. As a result, a market for artificial stones produced by labs started to flourish. More blue star sapphires becoming available in the market decreased the overall price of the stones, including natural ones. 

Although they are not “genuine,” lab-grown or artificial stones are incredibly convincing. Only trained professionals can tell the difference between a genuine gem and one manufactured from glass.

Red Star Sapphire

Technically, red sapphires are rubies. Rubies and sapphires are different colors of the natural mineral corundum, stemming from varying trace elements in the gem’s crystal lattice. What makes them different is that rubies are relegated to their characteristic red, while sapphires can vary in color from traditional blue to purple, green, white, or black. 

For that reason, you will more often find a red star sapphire in a store (properly) listed as star ruby. 

The price for a star ruby is relatively small other precious stones. You can find a 2.9-carat star ruby from Sri Lanka for as low as $80 (stone only).

Pink Star Sapphire

Scientifically speaking, a ruby is every precious stone with a trace of pink or purple. Gemologists worldwide generally differentiate between rubies and pink sapphires through subjective color divisions. In some cases, a gem might be called a ruby by one store and a pink sapphire by the other. Nevertheless, most stores typically classify gemstones as rubies when they exhibit an intense red color, while those with a more pinkish hue are typically categorized as sapphires.

Irrespective of the terminology used, the occurrence of pink coloration in corundum is uncommon in nature, especially in stones that exhibit asterism. As such, natural pink star sapphires can be prohibitively expensive, and you will likely find an artificial stone for sale.

One can find a 1-carat natural pink star sapphire from Sri Lanka for approximately $150.

White Star Sapphire

White star sapphires are more common than pink or green ones, but they can also be synthesized in labs. In the last decade, sapphires have become very popular among jewelry buyers. Natural white star sapphires are less expensive because they are more common in nature. 

White sapphires can cost up to $75 per carat. Lab-made sapphires have the same physical and optical properties, so it’s very hard for someone who wants to buy a white sapphire to tell them apart. 

Green Star Sapphire

As mentioned above, star sapphires occur in every color, but some colors are more difficult to find than others. Green star sapphires are so uncommon that the value of the very few in existence is incredibly high. The green hue comes from the presence of iron in the crystal. Despite numerous studies on the subject, there is no scientific consensus as to why the phenomenon of asterism is not more commonly observed in green gemstones.

Green sapphires are rare enough, imagine adding to it a 6-ray star. The majority of green sapphires found are typically in the range of light yellow-green to medium yellowish-green. However, as green sapphires are appealing in every shade, color saturation is not an important pricing factor. What makes them truly unique is that they are far more brilliant than emeralds. They are also more durable than other green gemstones such as peridot or tourmaline.

The high demand for green sapphires encouraged a market for lab-made gemstones. A Linde star sapphire in mind green may cost up to $500.

Purple Star Sapphire

Purple star sapphires are beautiful and unique gemstones. Any piece of jewelry with a bezel set purple star sapphire will automatically draw all the attention. Due to the popularity of these purple stones, many jewelers have created unique engagement rings with one in the center and a diamond halo to complement it. 

A 1.49-carat purple star sapphire that has been verified by the Gems Research Center and International Testing Laboratory costs $350. The price for engagement rings with this stone can range between $2,000 and $4,000. The cost will depend on the gem’s size, the ring’s setting (white gold, yellow gold, platinum, or other), and the quality of the diamonds that make up the halo. 

Talk to a Sapphire Expert

Ben and Afshin with customer in jewelry store in NYC

When planning to purchase a star sapphire, looking for as much information as possible is important. An even better way to learn about them is directly from an expert. Estate Diamond Jewelry has a team of professionals with years of experience in rare vintage jewelry collections. Contact a team member who will be highly qualified and pleased to assist you with acquiring unique gemstones.