While one side of the line is translucent, the other is milky. Gemstones that can exhibit this phenomenon: Chrysoberyl, tourmaline, aquamarine and moonstone. In this particular phenomenon, the gemstone exhibits a star pattern.
The difference between asterism and chatoyancy, is that in the latter there is only one parallel needle inclusion. Gemstones that display a sharp and distinct star with straight, even rays intersecting at the top middle part of the stone are highly valued. In addition to the three phenomena mentioned above, certain gemstones also exhibit the following. Also read — What Causes the Moonstone to Glow? Other gemstones that may show chatoyancy are:.
Asterism, like chatoyancy, is caused by reflection on inclusions. However, the inclusions are arranged in different directions causing several streaks of light on the surface of the en-cabochon stone. In general, the inclusions which cause the stars are orientated parallel to the crystal faces. There can be 4-pointed, 6-pointed and pointed stars. Diasterism is asterism caused by transmitted light from behind the stone and can be seen in some Rose Quartz and Almandine Garnet.
Asterism due to reflected light is named epiasterism , an example being pointed Corundum. Corundum usually forms 6-pointed stars mostly due to rutile or hematite needles. Emerald has been reported to show a 6-pointed star. You may also find in Corundum usually in Thai sapphire a pointed star due to rutile and hematite inclusions following both the 1st order and the 2nd order prism. This is an example of epiasterism due to reflected light.
The purity of the green is preferably modified with a bluish tone. If your stone changes from any color of purple to any color of blue , it is a synthetic Alexandrite-like Sapphire. An Alexandrite, whether it is natural or synthetic really Alexandrite, but man-made will change from some color of red to some color of green. The gold and orange shades of Sunstone identify with the Sacral Chakra, or Second Chakra , located below the naval and above the pubic bone at the front of the pelvis.
It controls the flow of energy and is the center of gravity of the body. The name Chatoyancy coming from the French to mean a cat's eye is when a parallel ray, that bares resemblance to the slit in a cat's eye, is seen on the surface of the stone. When the stone shows four or more ray this is known as asterism or a star.
Asterisms are patterns of stars of similar brightness. As Star Sapphire, Darnell can use her gem of power to fly and to hurl blasts of force nearly equal to the power of a Green Lantern's ring. The process of cutting and polishing gems is called gemcutting or lapidary, while a person who cuts and polishes gems is called a gemcutter or a lapidary sometimes lapidarist. Due to trace amounts of chromium in the structure, this gem can vary from bluish-green in daylight to purplish-red under incandescent light.
Though the discovery of alexandrite in Brazil and various other locations has expanded its availability, it still remains rarer than other gemstones , like diamonds. Musgravite was discovered in and is arguably the rarest gemstone in the world. While there may be many key differences between Alexandrite and diamond, but they are quite similar in value. Both gemstones are generally expensive and it is common to find Alexandrite jewelry that costs the same as diamonds.
Alexandrite is getting even more expensive due to its rarity as supply steadily declines. The gem type, the clarity of the star and number of star points — four, six or 12 — are factors that can influence its value. To highlight the star and show its optimal effect, the cutter will fashion the gem as a cabochon. Asterism occurs when light is reflected off inclusions of fine crystals or fibres that are orientated at specific angles to each other.
In turn, the strength and brightness of the star changes. Chatoyancy refers to sheen created by light reflecting off parallel channels, crystals or fibres included within the gem. Sheen is an important optical property that contributes to the beauty, value and desirability of many gemstones.
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