Asterism (gemology)

Under asterism (from Greek: ἀστήρ / aster / "star "), even light a star or star that shines called, is understood in mineralogy and gemology star-shaped reflections in crystals.

Produced the special light reflections through fine crystal fibers or needles that are stored in the respective host crystal and to meet with an ideal distribution in a point. And fine hollow channels in the rock are able to produce the star effect. The more uniform the fibers, needles or hollow channels are arranged, more harmonious and more beautiful works of light star. Depending on the crystal system and class of the relevant Minerals occur 4 -, 6 -, 12 - and 24 - ray stars on. When Rose Quartz can also circular asterism occur.

Asterism is preferably in sapphire and ruby ​​, the varieties " star sapphire " and " Star Ruby " have therefore been named after this effect. Also in synthetic gemstones asterism can be generated. However, while even the most beautiful natural starlight has a slightly irregular shape, man-made asterism is characterized by its too great perfection. The individual fingerprint of nature is lacking. By appropriate grinding ( cabochon ) of the asterism is emphasized.

Spread Tere and above all affordable stones with asterism form the so-called " star garnets " from the mineral group of the garnets. Grenade Although relatively rare form of asteroid rocks, but locally abundant occurring garnets are similar in each deposit very. There also exist spinels, aquamarines and moonstones with asterism.

You can see the asterism is usually only when a more or less point-like light source is directed onto the crystal. In evenly lit rooms with multiple light sources, the crystals appear unattractive.