Star sapphire is a variety of the gemstone sapphire that displays a reflected star of light on its surface. This phenomenon is called “asterism,” one of the optical effects that can make a gem “phenomenal.”
Are star sapphires real sapphires? Yep, star sapphire forms naturally.
What is the difference between sapphire and star sapphire? All star sapphires are sapphires, but not all sapphires display asterism.
This guide dives into all the stellar properties of star sapphire gemstones, from their meaning and benefits to grading and pricing.
Star sapphire is also called asteriated sapphire. As a sapphire variety, it’s a precious gemstone.
The mineral inclusions have different refractive indices than sapphire, reflecting light differently to create the star-like reflection. Most star sapphires have 4- or 6-rayed stars, though rare 12-rayed stars are possible.
Star sapphire’s mineral properties are below. For more specifics, check out our sapphire guide.
Color: All colors but red
Crystal structure: Hexagonal (trigonal)
Luster: Vitreous (glassy) to adamantine (diamond-like)
Transparency: Transparent to opaque
Refractive index: 1.757-1.779
Fracture: Conchoidal; Parting is common
Luminescence: Fluorescence present in all but black, green, and most blue sapphires (natural), varying degrees in all colors (synthetic); X-ray colors in some specimens
Pleochroism: Present & very strong in most colors; Color shifts depend on stone’s color
Next, what does a star sapphire symbolize?
Pictured above: Star of India sapphire | Image credit: Daniel Torres, Jr.
Sapphires are called the “gem of heaven,” and star sapphires take that celestial association to new heights, symbolizing dreams, potential, and hope.
Like stars themselves, star sapphires were historically used by travelers for protection and guidance. Some believed the stone would warn them of upcoming dangers.
Others believe star sapphires represent one’s Higher Self spiritually, granting clairvoyance.
Historically, some Christians called star sapphire the “Stone of Destiny,” associating the three bars (in six-rayed stones) with faith, hope, and destiny.
Among star stones, star sapphire is the archetype, often called the “asteria” in the past.
One of the oldest known star sapphires is the Star of India, a 563.35-carat Sri Lankan stone dated by American Museum of Natural History to be around 2 billion years old. It’s also one of the world’s largest gem-quality blue star sapphires.
The current largest blue star sapphire is the Star of Adam, another Sri Lankan specimen that weighs a whopping 1,404.49 carats.
The second largest star sapphire is the Black Star of Queensland, a 733-carat asteriated black sapphire found in Australia in 1938.
Most recently, the largest cluster of star sapphires, dubbed the Serendipity Sapphire, was uncovered in July 2021 weighing 2.5 million carats (510 kg).
Other purported healing properties include:
Recovery from illness
Sense of purpose
Enhanced psychic powers
Grading phenomenal gems like star sapphire involves both typical factors — color, cut, clarity, and carat weight — along with the stone’s rarity and quality of its asterism.
In terms of rarity, high-quality star sapphires are quite rare, raising their value.
Star sapphires form in every color but red, which is star ruby. The rarest colors are yellow, orange, or green. The most common are black, pink, or blue star sapphires.
What color star sapphire is most valuable? High-quality blue sapphires are most valued, both in star and non-star sapphires.
The star is usually white to gray. One exception is black star sapphires, which can have 12-rayed white and gold stars from hematite and ilmenite inclusions. The inclusions also make the stone, which is usually blue, green, or yellow, appear black or dark brown.
Muted star sapphire colors are less valuable than pure, saturated colors. This is partly because brighter colors better contrast the star. Certain colors’ popularity can also increase the price.
All star sapphires are cut as cabochons to properly display their asterism. The best cabochon cuts have a centered star, a dome around two-thirds of the gem’s width, and no unnecessary weight below the girdle.
If the girdle of the cabochon is oriented parallel instead of perpendicular to the c-axis, it can create a “cat’s eye” effect in some star sapphires.
Sapphires have Type II clarity, so minor visible inclusions are normal. Though silk inclusions cause star sapphire’s “star,” inclusions that obstruct the star, lower transparency, or cause worse coloring will lower value. Fractures and external blemishes also reduce value.
Star sapphires are almost never completely transparent; rare specimens with higher transparency are highly valuable. More translucent or opaque specimens are less valuable, though exceptional color can somewhat negate this.
Besides inclusions, asterism is graded on the star’s visibility and centering.
Visibility: The best star sapphires have straight, bright rays that are distinct and visible from a couple feet away. Muddled, wavy, or broken stars are less valuable.
Centering: The best stars are centered on the cabochon and consistently bright from all viewing directions.
The best stars are:
Uniformly bright from all directions
Centered on top of the stone
Go from girdle to girdle
Strongly contrasted with the sapphire’s color
As you rotate the stone, the star should move smoothly and elegantly.
That said, a star sapphire with greater translucence and highly saturated coloring but a weaker star can be more valuable than one with a better star.
Although many record-breakingly large sapphires are star sapphires, these stones are usually small. Black star sapphires are easier to find in large sizes. Star sapphire price-per-carat will increase between 0.5 to 1 carats and 1 to 5 carats.
Part of the reason for star sapphire’s rarity is that they’re often heated to be sold as more valuable transparent sapphires.
However, some heat, fracture-filling, and diffusion treatments can enhance the asterism. Treatments lower value and should be disclosed by the seller.
Are star sapphires lab-created? Sometimes, yes.
How can I tell if my star sapphire is real or synthetic? Here are some signs of synthetic star sapphires:
Flawless, perfectly uniform star
No imperfections (e.g. stripes of color, uneven bottom)
Very bright, evenly distributed color
“L” stamped on bottom (sometimes)
Star stays in the same spot as you move the stone around under a flashlight
Star sapphires form like other corundum minerals inside igneous or metamorphic rocks, crystallizing from cooling magma or metamorphism.
Inclusions can get inside the stone during formation, and if they’re the right size and orientation, they result in star sapphires.
Where are star sapphires from? The best star sapphires come from Sri Lanka and Myanmar. Other notable sources are Canada, Thailand, Cambodia, and India.
How much is a star sapphire worth? Depending on its gemstone properties, star sapphires can range from $10 to $10,000 per carat.
Here’s a general price breakdown for star sapphires by color and weight:
Fancy Color: $100-$300 per carat (0.5 to 1 carat); $100-$500 per carat (1 to 5 carats)
Blue: $20-$100 per carat (0.5 to 1 carat); $300-$1,200 per carat (1 to 5 carats)
Black: $10 to $30 per carat (0.5 to 5 carats)
The most expensive variety is near-transparent and pure blue with a sharp, distinct star.
Most star sapphires are quite durable, making gemstone care easy.
Fractures, abundant inclusions, and treatments like fracture-filling or diffusion make them weaker. Keep these types away from harsh chemicals or mechanical cleaning systems and opt for protective settings, especially for a star sapphire ring.
The safest cleaning method is with a soft toothbrush, warm water, and mild soap. Keep the stone away from acids and extreme heat.
Star sapphires are unique not only for their starry effect but also their rich lore and variety. There’s an eye-catching star sapphire for every style and budget, so find the one for you!
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