Back نجمية (علم الجواهر) Arabic Asterismus (Mineralogie) German Αστερισμός (ορυκτολογία) Greek Asterismo (gemología) Spanish Astérisme (gemmologie) French אסטריזם (גמולוגיה) HE Asterismo IO スター効果 Japanese Астеризм Kazakh Asterisme (mineralogie) Dutch
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An asterism (from Ancient Greek ἀστήρ (astḗr) 'star', and -ism) is a star-shaped concentration of light reflected or refracted from a gemstone. It can appear when a suitable stone is cut en cabochon (i.e. shaped and polished, not faceted).
A gemstone that exhibits this effect is called a star stone or asteria. The best known is star sapphire, but many other minerals can also be asteria, usually due to impurities in the crystal structure.