Star sapphire is a rare variety of sapphire that exhibits a rare asterism under specific lighting. When viewing star sapphire, a six-rayed star will appear to float across the surface of the stone. The effect is best viewed under a direct light source and while tilting and rotating the stone from different angles. Star sapphires contain unusual tiny needle-like inclusions of rutile. Aligned needles that intersect each other at varying angles produce the rare phenomenon known as asterism. Star sapphires can range in color from blue in various tones to pink, orange, yellow, green, lavender, gray, or black. The most desirable color is a vivid, intense blue.

Star sapphires can range in color from blue in various tones to pink, orange, yellow, green, lavender, gray, and black. The coloring agents in blue sapphire are iron and titanium, and vanadium in violet to purple colored stones. Star sapphires are cut en cabochon typically with very high domes to maximize the desirable star effects. The best cabochons are somewhat transparent to translucent, with smooth domes of good symmetry. One should look for an even roundness to the shape.

lighting. When viewing star sapphire, a six-rayed star will appear to float across the surface of the stone. The effect is best viewed under a direct light source and while tilting and rotating the stone from different angles. Star sapphires contain unusual tiny needle-like inclusions of rutile.