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Star Sapphires

A star sapphire is a corundum cut as a cabochon that shows a star of light on its dome, caused by light reflecting from fine needle inclusions arranged in three directions within the crystal. The star has six rays, or twelve where two sets of needles are present, and its sharpness and the body colour beneath it decide the stone. Byrex Gems offers star sapphires to the trade from Toronto, filmed unedited, with prices for approved buyers and viewings by appointment.

Where to buy star sapphires in Toronto

Byrex Gems lists 5 star sapphires online today. 2 of them come with a report from laboratories including GIA. Origins include Sri Lanka (Ceylon) and Burma (Myanmar). Viewings are at our Toronto office, 27 Queen Street East, Suite 407, steps from Queen subway station, by appointment. We have supplied coloured gemstones and natural fancy colour diamonds to jewellers and designers since 1988, and welcome private clients by appointment. Prices are shown to approved trade accounts; private clients can ask us on WhatsApp, where we reply within 12 hours, or by email within 24 hours. Every stone ships insured, worldwide.

Among the star sapphires listed today: 11.38 ct Star Purple Sapphire, GIA, Ceylon Unheated, 10.66 ct Star Oval Blue Sapphire, GIA, Ceylon Unheated, 5.74 ct Star Oval Blue Sapphire, Ceylon Unheated, 3.29 ct Oval Cabochon Star Sapphire, Burma Unheated, 3.18 ct Star Oval Blue Sapphire, Ceylon Unheated.

What makes a star sapphire

The effect is called asterism. Corundum grows with fine needles of rutile, called silk, aligned in three directions at sixty degrees to each other, following the crystal's symmetry. When a cutter shapes the stone as a cabochon with its dome perpendicular to the crystal's main axis, each set of needles reflects a band of light, and the three bands cross at the top of the dome as a six-rayed star. The star moves across the dome as the stone or the light moves.

A twelve-rayed star appears when a second set of needles is present, usually of a different mineral aligned at an angle to the first, so that two six-rayed stars overlap. These are uncommon and are prized when both stars are sharp.

Sri Lanka is the classic source, producing star sapphires in grey, blue, pale blue, pink and lavender from the same gravels as its faceted stones. Burma's Mogok valley produces fine blue star sapphires and star rubies with strong body colour. Thailand produces black star sapphires, whose star is formed by dark iron-bearing needles and shows gold or white against a black or very dark brown body. Australia, Madagascar, Tanzania and Cambodia contribute smaller quantities.

How laboratories describe star sapphires

A report identifies the stone as natural corundum, describes the body colour in plain terms, such as blue, greyish blue, grey or black, and notes that the stone displays asterism. It does not grade the star. Words such as sharp, well-centred and strong are the trade's, and the buyer judges them by eye.

The treatment finding is usually favourable, because heating dissolves the silk that makes the star, and a star sapphire that has been heated hard would lose its star. Most natural star sapphires are therefore unheated, and the report states "No indications of heating" or the laboratory's equivalent. Some stones are given gentle heat to improve body colour while keeping the silk, and the report states this. Diffusion treatment has been used to add a star to stones that lacked one, by diffusing titanium into the surface; laboratories detect it through inclusions, spectra and trace-element chemistry, and it must be disclosed.

Origin opinions are given where inclusions and chemistry allow, and Ceylon and Burmese stars have recognisable characters. Byrex star sapphires carry reports from GIA, GRS, SSEF, Gübelin, Lotus, AGL and others, each in its own wording.

What to check before buying a star sapphire

Judge the star first, under a single point of light such as a penlight or direct sun rather than diffused light, which weakens any star. The rays should be sharp, straight and of equal length, meeting at a single point centred on the dome, and the star should move smoothly across the stone as it is tilted. Rays that fade toward the edge, a star that sits off-centre, or a missing or broken leg all lower the stone.

Then judge the body. A star sapphire with strong, even body colour and good translucency is the ideal, but body colour and star compete: the silk that makes a sharp star also mutes the colour, and a stone with intense colour often has a weaker star. Buyers choose where the balance lies. Grey and pale blue bodies are common from Sri Lanka; fine blue is scarcer.

Check the cabochon. A high dome gives a stronger star; a heavy base adds weight without beauty and should be noted. Look for a flat, even base that will sit well in a bezel. Pairs are difficult, since two stones must match in body, star and dome. Corundum is hard and tough, and a cabochon in a bezel setting is a durable piece.

What drives the value of a star sapphire

The star and the body are weighed together. A sharp, complete, well-centred six-rayed star over a strong, even blue body with good translucency is the stone the market wants, and the combination is scarce because silk and colour work against each other. A fine blue body with a soft star and a grey body with a razor star are each worth less than the stone that has both.

Body colour ranks as it does in faceted sapphire: fine blue first, then pink, lavender and pale blue, then grey. Black star sapphires from Thailand are a market of their own, bought for a bright gold or white star on a dark body, and are judged on the star alone.

Twelve-rayed stars carry a premium when both stars are sharp. Treatment status matters as elsewhere: most stars are unheated, and a stone with a diffusion-induced star is a different and much lower article. Origin adds a premium for Burma and for Ceylon on fine stones. Size counts, since larger clean stones with a good star are uncommon. Cutting quality counts too, as a well-proportioned dome without excess base shows the star to its best.

Famous star sapphires and synthetic stars

The Star of India, a grey-blue star sapphire from Sri Lanka, was given to the American Museum of Natural History by J.P. Morgan at the start of the twentieth century, and apart from a short absence after a famous theft in 1964 it has been there since. It shows a star on both sides. The Star of Adam, a blue star sapphire mined near Ratnapura in Sri Lanka, was reported in 2016 as the largest known blue star sapphire. The Star of Bombay, a violet-blue star sapphire that belonged to the actress Mary Pickford, is in the Smithsonian, and the Black Star of Queensland, from Australia, is among the largest known black stars.

The synthetic star is the other thing to know. Synthetic star corundum was produced commercially from the late 1940s, sold under the Linde name, and has been made in quantity since. Its star is typically too perfect, sitting on the surface of the dome rather than appearing to float within it, and the body often shows curved growth lines under magnification. Laboratories separate it from natural by growth features and inclusions, and any star sapphire of importance should carry a report stating natural corundum.

Star rubies, star spinel and star garnet are different stones, and a report settles which is which.

Buying star sapphires from Byrex Gems

A Toronto house for the jewellery trade since 1988, Byrex Gems counts more than seven thousand jewellers, designers and dealers among its customers. Many of our star sapphires are accompanied by reports from GRS, SSEF, Gübelin, GIA and other leading laboratories, and each is filmed in our office so that you can judge it before it travels.

Prices are shown to approved trade buyers. For anything else, WhatsApp +1 (437) 450-3786 reaches us within hours, and info@byrex.com is answered the same day, seven days a week. What is listed is a part of what we hold: more star sapphires are kept in the vault, and what we do not hold ourselves we can source through our offices worldwide. Viewings are by appointment in Toronto, Hong Kong, Bangkok and Dubai.

Star Sapphires: questions buyers ask

What causes the star in a star sapphire?

Fine needle inclusions, usually rutile, aligned in three directions in the crystal. Cut as a cabochon with the dome set correctly, each set reflects a band of light and the bands cross as a six-rayed star. A second set of needles produces a twelve-rayed star.

Are star sapphires usually heated?

Most are not, because heating dissolves the silk that forms the star. Some receive gentle heat to improve body colour and the report states it. Diffusion has been used to induce a star in stones that lacked one, and laboratories report it; it must be disclosed.

How do I judge a star sapphire's star?

Under a single point of light. The rays should be sharp, straight, of equal length and centred on the dome, and the star should move smoothly as the stone is tilted. A missing or broken ray, a star off-centre or one that fades at the edges lowers the stone.

Where do star sapphires come from?

Sri Lanka is the classic source for blue, grey, pink and lavender stars. Burma produces fine blue star sapphires with strong colour. Thailand produces black star sapphires. Australia, Madagascar, Tanzania and Cambodia contribute smaller quantities. Origin on a report is an opinion based on inclusions and chemistry.

What is a black star sapphire?

A corundum with a black or very dark brown body whose star is formed by dark iron-bearing needles, showing gold or white against the body. Most come from Thailand. They are judged on the star alone and form a market of their own.

Does a report show whether a star sapphire is synthetic?

Yes. A laboratory separates them through growth features and inclusions. Synthetic stars, made commercially since the late 1940s, tend to show a star that is too perfect and sits on the surface, with curved growth lines in the body. A report stating natural corundum is the basis of any sale.

Does Byrex source star sapphires for private clients?

Yes. Byrex sells to the jewellery trade and receives private clients by appointment. Star sapphires are shown with their laboratory reports, under a point light so the star can be judged, and a particular body colour or size can be sought through Byrex's suppliers.

Can I view star sapphires in Toronto?

Yes. Byrex Gems shows stones by appointment at 27 Queen Street East, Suite 407, Toronto. A star should be judged under a single point of light and in daylight, and unedited footage of each stone is available to shortlist beforehand.

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