Single Refractive Gems
One of the main properties of a gemstone is its refractive index. This is the property, when light passes from one medium to another; the light rays are refracted or bent at an angle. This is the reason why a straw in a glass of water appears to be bent. Each substance has its own refractive index. This is also quite useful for some gemstone identification. The refractive index of a particular material is expressed as the speed of light in vacuum divided by the speed of light through the particular material.
Water has a refractive index of 1.33 and diamond has a refractive index of 2.417 to 2.419.
Some gemstones have single refractive index; they have only one refractive index. Other gemstones have double refractive index; mean they have two different refractive indices. When a beam of light passes through a double refractive gemstone, it gets split into two beams, each of them travelling at a different speed and on a different path through the crystal.
Birefringence is a measurement which is used to find the difference between the two refractive indices in gems that have double refractive property. The best known are diamond, garnet and spinel.
Organic Natural Amber
It is found in the shape of cube. Cubic solids are symmetrical and they have three perpendicular axes. This is the reason; they refract light in all directions at the same velocity. It includes diamond, garnet and spinel, but fluorite, lapis lazuli, sodalite and pyrite also comes under this category.
Gems that are amorphous have no definite crystal structure and they are single refractive. They belong to several subcategories such as opals, natural glass, and organic gems. The members of the opal family are common opal, fire opal, boulder opal and precious opal.
Natural Glass Obsidian
These two are amorphous because they are formed under conditions of rapid cooling which further prevents crystal growth.
The organic gems include amber, ivory, pearl, jet and ammolite. Amber and Jet are derived from the plant materials while ivory, pearl and ammolite have their own source in animal kingdom. Some gems that are from animal source are coral or petrified wood. These are crystalline, since the original organic material has been replaced by jasper or chalcedony.
These gemstones give very long term effect to the wearer. All these gemstones have some invisible rays that help the wearer to fight from the negative situations of life. If you’re wearing a semi-precious gemstone, there is nothing to fear because they are harmless. Yes, for wearing a precious gemstone, you should consult an expert astrologer