Star Sapphires are a unique variety of precious stone which 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 give you a thorough introduction to star sapphires, their origin, hues, treatments, and price.
What Is a Star Sapphire?
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 composition of the mineral rutile is primarily 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 will move slightly with the light source when the stone is turned around, yet another unique feature of a star sapphire.
For a more prominent star, these sapphires are always cut into a high dome cabochon shape (French: en cabochon), which also draws attention to any piece of jewelry 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 can be found in a wide variety of colors besides the characteristic deep blue. They are currently located 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
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
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 be described as 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. For these purposes, 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?
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 stone’s distinctive qualities will affect the cost. The largest blue sapphire in the world, known as the Star of Adam, measuring 1,404 carats, 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?
For the asterism phenomenon present in star sapphires to occur, the needles of rutile need to be packed tightly in parallel lines. 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.
Though six-ray star sapphires are uncommon compared to traditional sapphires, there is an even more unusual 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.
The most common colors for star sapphires are black, pink, and blue, but it’s not fully understood why these gems are likelier to contain rutile.
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. In some cases, the recreation is so refined it’s challenging to distinguish a real gemstone from one out of the lab.
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 can be seen even in low light and does not move 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
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. However, most stores usually classify rubies as intensely red, and coloration that settles more on pink is reserved for sapphires.
Regardless of what they’re called, pink coloration in corundum is rare in nature, let alone for stones with asterism. As such, natural pink star sapphires can be prohibitively expensive, and you will likely find an artificial stone for sale.
A 1-carat natural pink star from Sri Lanka can be found for sale at $150.
White Star Sapphire
White star sapphires are more common in nature than pink or green ones, but they can also be grown in a lab. In the last decade, sapphires have become very popular among jewelry buyers. Star sapphires are now unique stones bezel set in earrings, necklaces, and engagement rings. 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. While there’s been plenty of studies made on the subject, there is no scientific consensus as to why the asterism phenomenon doesn’t occur more often in green gemstones.
Green sapphires are rare enough, imagine adding to it a 6-ray star. Most green sapphires in existence range from light yellow-green to medium yellowish-green, which can be described as olive or leaf 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
When planning to purchase a star sapphire is important to look for as much information as possible. An even better way to learn about them is directly from an expert in the subject. Estate Diamond Jewelry has a team of professionals with years of experience in rare vintage jewelry collections. Get in touch with a member of our team, who will be highly qualified and pleased to assist you with acquiring unique gemstones.