Star sapphire price: what a star sapphire is worth per carat
Star sapphire is valued for asterism — a sharp, centred star of light gliding across the dome. The clarity of that star, plus body colour, sets the price.
What drives star sapphire price
Star sapphire shows asterism: a rayed star (usually six-legged) caused by fine needle inclusions, seen in a cabochon under a single light. Value depends on the sharpness, straightness, completeness and centring of the star, combined with an attractive body colour.
Star quality & body colour
The best stars are sharp, complete and perfectly centred, gliding smoothly as the stone tilts. A strong blue body with a bright, sharp star is the classic top combination; fine pink, grey and black star sapphires also occur. The needle inclusions that create the star also make the stone somewhat translucent — the balance between transparency and a bold star matters.
Treatment & a caution
Some star sapphires are heated or diffused, and diffusion-induced stars exist and are far less valuable — a lab report is worthwhile for fine stones. Large stones with a sharp, well-centred star and good colour are scarce and premium.
Star Sapphire price — frequently asked questions
What makes a star sapphire valuable?
A sharp, complete, well-centred star combined with an attractive body colour and reasonable transparency. Weak, off-centre or partial stars reduce value.
Why do star sapphires have a star?
Fine parallel needle inclusions (usually rutile "silk") reflect light into a rayed star, an effect called asterism, best seen in a cabochon under a single light source.
Are star sapphires treated?
Some are heated, and diffusion can induce or sharpen a star artificially. Diffused-star stones are much less valuable, so a lab report is worthwhile for fine material.
How much is a star sapphire per carat?
A sharp star with strong colour in a larger size commands the highest prices; weak stars are inexpensive. Use the calculator to estimate your stone.
Indicative trade information from the Gem Index universal pricing engine — not a formal appraisal or laboratory certificate. Wholesale, USD. Species, treatment and origin should be confirmed by an accredited gem laboratory before sale. See our full disclaimer and methodology.