An Aurora Borealis or the Northern Light is a natural light display in the sky, particularly in the polar regions and usually occuring at night, caused by the collision of charged particles directed by the Earth’s magnetic field.
The optical phenomena of gemstones with this ‘Northern Light’ has a shimmering blue aurora called Adularescence and is most prominent in Moonstones. The effect is best described as a billowy, milky and bluish luster or glow originating from below the surface of the gemstone. The scattering of light in Moonstone is actually caused by the intergrowth of 2 kinds of crystallized alternating layers, hence, when light is directed at a moonstone, light is scattered off in all directions instead of bouncing off the normal and reflected or refracted in one direction.
The degree of the billowy light of the adularescence is determined by the thickness of the intergrown layers. Here, thin layers may produce the most desirable bluish adularescence while thicker layers will give the gemstone a whitish adularescence.
Some Moonstones also exhibit the chatoyancy phenomena of cat’s eye and they are much sought after by connoisseurs when the tantalizing bluish light shimmers on the surface with a clear distinct cat’s eye.
Adularescence also appears in numerous other gemstones, notably common opal, rose quartz and colorless quartz. However, due to inclusions in these other stones, the effect is displayed differently.
http://farm4.static.flickr.com, http://i.telegraph.co.uk, http://www.crystals11.com, http://www.mardonjewelers.com, http://www.gemstoneslist.com, http://www.djraregems.com, http://en.wikipedia.org
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