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What is Phenomena in Gemstones and how does it impact value?


Have you ever wondered why some gemstones show different and sometimes dazzling effects (phenomena)?

These gemstones, and there are many of them, show phenomena as light interacts with their structure, Opal, Moonstone, Alexandrite, Star Sapphire and Ruby are just a few. These spectacular gemstones phenomena colors seem to dance both on the outside and inside of the gemstone basic color. It is fair to say that the stronger the phenomena the more valuable the gemstone is.

Lets take a look at five of the more common gemstones with Phenomena


This gemstone is known for its play-of-color, so what is play of color it can be described  as a shifting flash of rainbow colors. Most gemstones are crystals but Opal is made up of spheres of Silica, the size of the spheres, their alignment and the way light interacts with them provide the shifting color the eyes see.

 The value of an Opal is dependant on the color and the strength of play-of-color, today the most prized and valuable opals have a black body color and with large and distinct patches of many bright and intense colors that  are called Harlequin. The more common opal sold today in jewelry stores is the White Opal, it cost is lower and you still see this play of color although it lacks the intensity of the black opal with a Harlequin patchwork of bright colors


This gemstone will show a Phenomenon called Adularescence, and can best be described as billowing color that is different from the body color and seems to float across the moonstone. It is a very striking effect. Moonstone is the only natural gemstone to display adularescence and relatively inexpensive, the next time you are looking for an interesting gemstone take a look at this phenomenal stone

Value is based on the body color, which should be light blue with a bright blue adularescence, this is followed in value by a white body color with a blue adularescence and finally by the moonstone with either a grey or white body color.


This gemstone is know for its dramatic color change, which depending on the change in light, can change the color of the gemstone from green to brown, blue to red, and many other combinations. While there are other natural gemstones that have color change such as Garnet, Sapphire, Ruby, Spinel, this gemstone has come to be known for its dramatic changes and you will sometimes hear the term “alexandrite effect”

The more valuable color change Alexandrite will change colors from green to a purplish red with a medium saturation in both hues. If you want a color change gemstone and don’t want to pay the prices that Alexandrite command look at a color change garnet, its relatively inexpensive and provides a distinct color change for you to see and admire.

Star Ruby, Star Sapphire

Some gemstones have a phenomena call asterism, which produces a star on the face of the gemstone when the light hits the surface. There are quite a few gemstones with Asterism but you will probably hear more about Star Sapphires and Rubies. Most Gemstones with asterism will either show a 4 or 6 ray star this is due to the crystal structure of the gemstone.

Value is determined by the quality of the star rays as they should be straight and reach all the way across the gemstone. Most Gemstones with Asterism are cut as cabochons with high domes to distinctly show the star. Star Ruby, Sapphire and Garnets are the most expensive, but if you are looking at something less costly look at the Black Star Sapphires.

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Derek Parnell is a Graduate Gemologist (GIA) and owner of Jewels by Truros a division of Truros Corporation. Truros Corporation has interests in the Jewelry and the Real Estate Industry. For more information you can reach Derek at  Jewels by Truros.


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