The ring you've shared features a striking blue stone that, while it shares some visual traits with a star sapphire, is more commonly identified as a blue "star" art glass imitation. These pieces often appear in vintage Art Deco or Art Nouveau jewelry, particularly from the 1920s and beyond.
Key Characteristics Material: It is likely a molded blue glass, sometimes referred to as "star glass" or "moonglow" glass, rather than a natural gemstone. Visual Effect: The "star" in these glass pieces is typically fixed and molded into the glass itself. In contrast, the star in a genuine star sapphire is an optical phenomenon (asterism) that moves across the surface as the light source or the ring is turned. Setting: These stones are frequently set in sterling silver, often with intricate Art Nouveau or Art Deco designs. Similar designs have been attributed to antique Czech craftsmanship