>> Tuesday, January 6, 2009
Each Gemstones have some special effects. These effects are either natural - called “phenomena” by gemologists - or created by the special cutting and shaping techniques. These special techniques gives brilliance to the defiance of the stone itself and give optical impression. Below there is a list of popular gemstone effects that describes the definition of better stone:
Fire- Color of highlights because it is the ability of the stone to draw light apart into its constituent colors, due to dispersion. Zircon and diamond are among those stones that show elaborated fire abilities.
Schiller is also known as play of color, which shows the flickers of color inside the stone when stone is moved in the light. Opal is especially valued for this trait. There is no actual object inside the stone. This special effect arises from light interference within the microstructure of the mineral.
Fluorescence is the ability of a mineral to turn incoming light of ultraviolet color into light of a visible color. Is a condition of vigor and freshness. A special effect like this is desirable to transform the dull color of a stone to a different glow.
Labradorescence is the effect that arises from light interference within microscopically thin layers of twinned crystals. The sizes and orientations of these twin lamellae are consistent in this feldspar mineral, thus colors are considered strong and limited with regards to its direction and orientation.
5. Color change
Some gemstones changes color when put in different aspects of light especially when placed in front of sunlight. This is due to a gemstone’s ability to absorb wavelengths strongly. Change of color is not the same as the changes in color with crystal orientation that affects tourmaline and iolite, which are due to the optical property called pleochroism.
Iridescence implies all sorts of rainbow effects ( schiller and labradorescence are varieties of iridescence ) Mother-of-pearl is the most familiar example of iridescence, but it is also found in fire agate and some obsidian as well as many artificial gems and jewelry.
7. Cat’s Eye
Derived from the French term “chatoyance”. Cat’s eye is caused by impurities within the gemstone arranged like fibers and line up forming axes. Quartz is famous for its cat’s eye property when struck by light. Traces of fiber within the mineral give this effect a special twist.
Inclusions in a gemstone are usually considered flaws. But in the right kind and size, inclusions create internal sparkles, particularly in quartz (aventurine) where the special effect is called aventurescence. Thousands of tiny flakes of mica or hematite can turn plain quartz into a glittering rarity or feldspar into sunstone.
Opalescence is also called adularescence and milkiness in other minerals. It can be a white haziness or soft colorations. Opal, moonstone (adularia), agate and milky quartz are the gemstones best known for this special effect.
When fibrous inclusions align on all of the crystal axes, the cat’seye effect can appear in two or three directions at once.