In Buddhism it is considered one of the seven treasures and equated with wisdom . The word "emerald" comes from the Latin smaragdus , coming from the Greek smaragdos , but its original source is a Semitic term, izmargad , or a Sanskrit term, maragata , which literally means "emerald".
It is of the dimetric crystal group and hexagonal system. Its chemical formula is equivalent to Be 3 Al 2 Si 6 O 18 , that is, beryllium , aluminum , silicon and oxygen together with chromium . Emeralds are graded using four basic parameters: color, cut, integrity and transparency . The most important aspect of the gem is certainly the color , followed by transparency . A good specimen must in fact have not only a pure green hue, but also a high degree of transparency to be one of the best in the world.
Emeralds tend to have numerous inclusions and cracks on their surface. Unlike diamonds , where integrity is measured using a standard 10x loupe, emeralds are measured with the naked eye. Thus, if an emerald has no cracks visible to the naked eye, it is considered flawless. Stones that lack a cracked surface are extremely rare, and so almost all emeralds are "oiled" to improve their apparent integrity.
Because of this treatment they cannot withstand extreme temperatures. Whole emeralds to the naked eye have a vivid shade of green with no more than 15% of any secondary color (either blue or yellow) with a medium-dark shade to command the best prices. These non-uniform aspects make emeralds more similar to other gems when cut into cabochons, rather than facets.