Star Rubies and Sapphires have been documented since the 1500s, and treasured as special talismans ever since. Asterism can sometimes also be seen in Garnet, Spinel and Diopside although they are significantly less popular.ġ5.02 Carat Blue Star Sapphire and Diamond Ring in 18ct White Gold, Stars can appear in any Sapphire colour, including blue, grey, black, purple, yellow, and red (which are Star Rubies), and must be cut into a cabochon shape in order for the asterism effect to be seen.

In very rare conditions, multiple sets of these inclusions can even form a 12-pointed star. Singularly, this creates the cat’s eye effect, however when there are multiple groups of rutile inclusions, each formed in parallel to each side of a Ruby or Sapphire’s six crystal sides, multiple distinct lines of light can appear and form a six-pointed star. However, when the entire gem features these tube-like inclusions and they are highly uniform and parallel, they can reflect a straight and sharp line of light, similar to how a spool of thread does. This group often creates the effect of “silk” in a gem, since the inclusions diffuse light and often give the surface of the gemstone a lovely silky appearance. However, in the case of cat’s eye and asterism effects, they form in a such a rare and unique way that they create a very special collector’s piece.Īsterism is created when long, thin, tube-like inclusions (often called rutile inclusions) form in a large group. Inclusions are often considered a negative effect, as they often take away from a stone's natural perfection. Similar to cat’s eye gems, the effect of asterism is actually caused by a rare collection of inclusions. Phenomenal gems are those that feature very special optical effects, such as, Opal’s play-of-colour, Cat’s Eye Chrysoberyl, Moonstone, colour-change gems such as Alexandrite, and of course, Star Rubies and Sapphires.

The gem phenomena of asterism doesn’t come along everyday-here’s everything you need to know about rare and precious Star Sapphires.

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Blue star sapphire