Star Sapphire Gemstone Guide
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You might be familiar with the beautiful sparkling face of the traditional blue sapphire. But this article will focus on a lesser-known variety of sapphires: star sapphires. These refer to gemstone-grade sapphires that feature a white or golden star across their center. This phenomenon is called ‘asterism’.
In this guide, we will examine star sapphire gemstones in detail, including the different color varieties and how to care for them in jewelry settings.
About Star Sapphire
As mentioned, a star sapphire gem displays asterism, an optical phenomenon that creates a star-like pattern on the surface of the stone. Star sapphires are one of only six varieties of unique gemstones that are associated with asterism, the others being star rubies, star garnets, star diopside, star spinel, and star quartz.
Star sapphires typically display a six-rayed star caused by rutile needle inclusions. They are highly prized and come in various colors, including blue, pink, and green.
Gemstone Properties and Characteristics of Star Sapphire
Star sapphires are a type of corundum composed primarily of aluminum oxide. The presence of rutile inclusions is what differentiates them from other sapphires. Rutile inclusions are mostly composed of titanium dioxide, which causes the star-like reflection on the surface of these gems.
This effect, known as asterism, is caused by the reflection of light from the needle-like inclusions of rutile within the gemstone. These inclusions are aligned in such a way that they create a star pattern, typically with six rays, although twelve-rayed stars can occur in rare cases.
Most star sapphires are cut en cabochon—a smooth, rounded shape without facets—to highlight the star. This cut allows light to interact optimally with the rutile inclusions and makes the gemstone stand out in a jewelry setting.
While blue is the most common and popular color for star sapphires, they can also be found in other colors such as orange, yellow, green, purple, and black. Pink sapphire star gems are also available. The color can influence the stone’s value and appeal.
Like other sapphires, star sapphires are highly durable with a hardness of 9 on the Mohs scale, making them suitable for everyday wear. They are mined in Malawi, Zimbabwe, Rwanda, Pakistan, China, Kenya, Vietnam, Tanzania, the United States, Madagascar, Cambodia, Brazil, Sri Lanka, Thailand, Myanmar, and Australia.
Here is an outline of some important gemstone properties for star sapphires for quick reference:
- Streak: White (although Thailand varieties have a golden star)
- Fracture: Conchoidal with parting in many cases
- Transparency: Opaque is common, some transparency might be present
- Luster: Adamantine (diamond-like) to Vitreous (glassy)
- Color: All except red
- Mohs hardness: 9
Star Sapphire Meaning and History
Star sapphires are imbued with rich symbolism and are believed to possess a variety of healing properties. Historically, these gemstones have been revered as protective talismans, offering guidance and safeguarding travelers from harm. In ancient cultures, star sapphires were associated with divine protection and were thought to repel negative energies. The unique star-like pattern seen in these stones is often linked to celestial constellations, symbolizing hope, destiny, and spiritual insight. In Christianity, the star’s rays are interpreted as symbols of faith, hope, and charity, earning the star sapphire the title ‘Stone of Destiny’.
History
Star sapphires have been mined for centuries, particularly in Sri Lanka, which is renowned for its rich gemstone deposits, including sapphires. The region of Ratnapura in Sri Lanka, known as the ‘City of Gems’, has been a significant source of these stones for over 2,000 years. The oldest known star sapphire specimen is the Star of India, which is estimated to be around two billion years old. It is housed in the American Museum of Natural History in New York.
The largest-known star sapphire to ever be unearthed is the Star of Adam, weighing 1,404.49 carats. It was discovered in Ratnapura, Sri Lanka, in 2015 and is valued between $100 million and $300 million. The second-largest star sapphire in the world is the Black Star of Queensland. This 733-carat sapphire was found in 1930 in Australia.
Star Sapphire Grading Factors
When it comes to grading special gems like a star sapphire, there is more involved than just the gem’s carat weight, clarity, cut, and color. You also have to factor in the quality of the asterism and the size of the stone.
Below, you can find a breakdown of the key factors that are considered in a star sapphire appraisal.
Carat Weight and Size
Carat weight plays a significant role in determining the value of a star sapphire, as larger stones are rare and often coveted. As a result, the price-per-carat for these stones typically rises as the carat weight increases, though this is contingent on maintaining high quality in the other grading aspects.
Asterism: Centering and Visibility
Asterism is graded according to the star’s visibility; a well-defined star significantly enhances the sapphire’s value. The star should be clearly visible under a single light source and exhibit movement across the stone’s surface when rotated. Broken, wavy, or poorly centered stars decrease a stone’s value. High-quality star sapphires are exceedingly rare, so they often fetch premium prices when they appear on the market.
The very best stars:
- Have bright rays that contrast strongly with the color of the sapphire.
- Are uninterrupted.
- Run from girdle to girdle.
- Are centered on the stone.
- Are smooth.
- Are intact.
- Have straight arms.
- Are uniformly bright.
Remember, a star sapphire’s value is not solely dependent on the brilliance of its star. The sapphire’s color and translucence also add to its value.
Transparency and Clarity
The clarity of a star sapphire is never entirely perfect. This is because some inclusions are necessary to create the star effect. In other words, minor visible inclusions are acceptable for these stones. However, any inclusions that obscure the star or affect the body color of the sapphire will lower its value.
The presence of rutile inclusions not only creates the star effect but also gives many star sapphires a milky or ethereal appearance. Thus, how translucent a star sapphire is will also impact its price.
Cut
Most star sapphires are cut into cabochon shapes to enhance the visibility of the star pattern. When the star is centered, the cabochon is considered high quality. Where the girdle of the cabochon is can also impact how the stone looks, and can sometimes give the star the appearance of a cat’s eye. Proper cutting is, therefore, essential to preserve the image of the star.
Color
While the visibility and quality of the star pattern are important, the color of a star sapphire often has a greater impact on its value. The most prized star sapphires are those with saturated colors and well-defined stars that appear to float across the stone’s surface when viewed under a single light source.
One of the reasons for this is that a bright color often contrasts better with the star, making it more visible and eye-catching in a jewelry piece like a ring. Some colors are also more popular for star sapphires in general. For example, blue star sapphire is more popular than orange. The same holds true for sapphire gems without asterism. Generally, blue sapphires are the most valuable, regardless of whether they display the star effect or not.
Like every other sapphire, star sapphires are available in several colors except red (the red variety of the mineral corundum is called ruby). Blue, black, and pink star sapphires are quite common, whereas orange and yellow are rarer. Interestingly, black star sapphires are not actually black. They are usually green, yellow, or blue but appear black due to inclusions.
Star Sapphire Simulants and Synthetics
Occasionally, you might come across a particularly high-quality star sapphire for sale. When this happens, you might be looking at a synthetic or lab-created gemstone. Lab-created star sapphires tend to look too perfect to be real and might cost less than what you would expect to pay for a natural specimen. However, you also get natural gemstones that have been treated to artificially induce the famous star effect and intensify the color of the stones.
In most cases, you would need the help of a professional jeweler to differentiate between a natural, man-made, or treated star sapphire, but there are some tell-tale signs you can look out for when shopping for one of these gems.
Most notably, look for the following characteristics when identifying synthetic star sapphires:
- The star does not move when the stone is moved around.
- Sometimes there is an ‘L’ stamped on the bottom.
- The color is distributed evenly and is very bright.
- There aren’t any imperfections.
- The star is uniform and flawless.
In addition to synthetic star sapphires, you also get simulant gems that consist of a star rose quartz with a blue backing, giving them the appearance of a blue star sapphire.
Star Sapphire Color Varieties
Star sapphires owe their colors to various trace elements within the corundum mineral structure.
Purple Star Sapphire
The purple hue in star sapphires is typically due to the presence of chromium and iron, with titanium sometimes contributing to the color. Purple star sapphires are less common than blue but not as rare as green, with prices generally lower than those for blue or green stones.
Green Star Sapphire
Green star sapphires are colored by iron impurities, which can produce a range of green shades. Green star sapphires are among the rarest, making them highly sought after and expensive, although specific price ranges can vary significantly due to their uncommon nature.
White Star Sapphire
White star sapphires are generally colorless and derive their appearance from rutile inclusions rather than specific trace elements. White star sapphires are typically less expensive due to their more common occurrence and lack of vibrant color.
White sapphires are often used as a cheaper alternative to diamonds in engagement rings and other types of jewelry like necklaces and earrings. A white star sapphire would work just as well in these jewelry settings and offers something a bit different to the traditional faceted gem with their cabochon cut.
Pink Star Sapphire
Pink star sapphires owe their color primarily to chromium, with iron and titanium potentially influencing the shade. Pink star sapphires are also relatively common but can be quite valuable due to their unique coloration, with prices varying widely based on quality.
Some pink sapphire may also be classified as ruby depending on the shade and intensity of the pink. However, this typically only applies to stones that exhibit a deep shade of red.
Red Star Sapphire (Star Ruby)
Red star sapphires are not technically sapphires but are classified as rubies, with their red color resulting from chromium impurities in the crystal lattice of the gem. Another type of red star gem is the star garnet, which is frequently mistaken for ruby.
Red star sapphires, or rubies, are highly valued for their intense color and rarity, often commanding high prices similar to or exceeding those of blue sapphires.
Blue Star Sapphire
Blue star sapphires are colored by the combination of titanium and iron impurities, which create the classic blue hue through intervalence charge transfer (IVCT). This process involves the transfer of electrons between different metal ions within the crystal structure, specifically between iron (Fe) and titanium (Ti) ions. In other words, when light hits a sapphire, an electron moves from an iron ion to a titanium ion, changing their oxidation states. This electron movement results in the absorption of certain wavelengths of light, which gives the sapphire its characteristic blue color.
In terms of rarity and cost, blue star sapphires are the most common and highly valued, often priced between $800 and $1,200 per carat for high-quality stones.
Star Sapphire Care and Maintenance
Caring for star sapphire jewelry, such as a star sapphire ring, involves several steps to ensure its longevity and brilliance. First and foremost, it’s important to avoid exposing the gemstone to extreme heat, as this can potentially damage the stone or alter its color. Star sapphires are generally durable due to their hardness, but sudden temperature changes can cause internal stress and lead to cracks or other damage. When you’re not wearing your star sapphire jewelry, store it in a soft cloth pouch or a separate compartment in a jewelry box to prevent scratches from other pieces.
For cleaning, use a soft toothbrush along with mild soap and warm water to gently remove any dirt or oils that may accumulate on the surface of your star sapphire. This method is effective in maintaining the stone’s luster without causing damage. Avoid using harsh chemicals or abrasive cleaners, as these can harm the gemstone and its setting. After cleaning, rinse your jewelry thoroughly with warm water and dry it with a soft cloth. Regular cleaning will help preserve the beauty of your star sapphire jewelry while ensuring that the distinctive star pattern remains visible and vibrant.
Frequently Asked Questions
Is a star sapphire a real sapphire?
Just like traditional sapphires, star sapphires are a variety of the mineral corundum. They exhibit the same fundamental crystal structure and hardness as other sapphires. The only difference is that star sapphires display asterism, which is the star-like pattern on the stone’s surface caused by needle-like inclusions of rutile within the crystal. These inclusions do not alter the sapphire’s essential mineral composition, confirming that star sapphires are indeed real sapphires.
How much is a star sapphire worth?
The price of a star sapphire is determined by several key factors. These include the size and quality of the gem, which encompasses its color, clarity, and cut. It also considers the quality of the gem’s star – a stone with a well-defined star consisting of bright, evenly distributed rays will be worth more than one with a broken or muddled star.
Where are star sapphires mined?
Star sapphires are mined in several regions around the world, including Australia, Thailand, and Madagascar. However, the best star sapphires come from Sri Lanka and Myanmar (modern-day Burma).
Are there other gemstones that display asterism?
Asterism is quite a rare phenomenon that does not commonly occur in nature, so only a handful of other gemstones besides sapphires sometimes display stars. These include garnets, rubies, diopside, spinel, and quartz.
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