You are in Polish, brilliance and fire: all about gems.
These terms are often used in an improper manner even by professionals with experience.
Are primarily used to describe the interaction between light and gem and deepening the following we will explain in detail the different aspects of these characteristics of each gem, so trying to give useful advice and guidance on how to navigate the selection of the best gems.
Polish The polish is the amount and quality of light reflected from the surface of a gemstone and is a function that indicates the refraction and the perfection of the surface, ie the enamel. If the light that falls on a gemstone is reflected in large quantities then you will have a stone with high luster. If instead the gem absorbs most of the light, resulting in reflection opaque, then the luster will be of low intensity. Other terms commonly used for the splendor of the gems are:
Metallic: This is demonstrated by the very high gloss metals such as gold and silver and gems such as hematite and pyrite.
Adamantine: A singular feature of diamond, is very bright and reflective, almost metallic. The descriptive term sub-adamantine is often used to describe gems with gloss close to diamond, such as demantoid garnet. Vitreous: The luster of gems more transparent whose refractive indices falling in the middle range of values, such as Emerald and Tourmaline.
Softwood: Some gems which have a low refractive index, such as amber, which are having a resinous luster.
Brilliance The gloss refers to the amount of light that is perceived by the return from the inside of the gem and is mainly a fusion of refraction, proportion and transparency. The faceted stones are precisely designed to capture all possible light and throw it back. If the stone is cut incorrectly, maybe in too deep or shallow, the brightness will suffer a lot. We learned in the previous chapter, however, the splendor that an excessive level of refractive index could lead to damage to the perception of color. The right compromise is to find stones with good proportions, not too low nor too deep.
Fire The fire, or dispersion, is the separation of light into component colors namely red, orange, yellow, green, blue and purple. When light passes from one medium to another its individual colors are folded in different sizes. The resulting effect is that the light will not appear whiter but it will be split into different colors. The dispersion is also given on the size of the gem which of course will cause more or less possible paths for the light in the same stone.