mineral

Star Ruby

Corundum (Al2O3 with chromium and rutile inclusions)

Hardness: 9.0; Color: Pinkish-red to deep red; Luster: Adamantine to vitreous; Crystal system: Trigonal; Features an 'asterism' (6-rayed star) caused by needle-like rutile inclusions.

Hardness: 9
Color: Pinkish-red to deep red
Luster: Adamantine to vitreous

Identified April 15, 2026More mineral →

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Physical properties

Hardness: 9.0; Color: Pinkish-red to deep red; Luster: Adamantine to vitreous; Crystal system: Trigonal; Features an 'asterism' (6-rayed star) caused by needle-like rutile inclusions.

Formation & geological history

Formed in metamorphic or igneous environments, particularly marble or basalt. The 'star' effect requires millions of years of gradual cooling to allow rutile needles to align perfectly.

Uses & applications

Primarily used in high-end jewelry (cabochon cut) and as a valuable collector's gemstone.

Geological facts

Star gems like this ruby are usually cut into a cabochon (smooth, rounded shape) rather than faceted to ensure the star is visible. It is the birthstone for July.

Field identification & locations

Identify by a 6-rayed star appearing under a single point of light that moves as the stone is tilted. Generally found in Myanmar, Sri Lanka, and Africa.

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Mineral/Rock

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mineral