EMERALD

Emerald is a gemstone and a type of beryl (Be3Al2(SiO3)6) that has been tinted green by minute amounts of chromium or, occasionally, vanadium.  The Mohs scale rates beryl's hardness as 7.5-8. The majority of emeralds are strongly included, making them generally weak in terms of toughness (resistance to breakage). Cyclosilicate is what makes emerald.

 

The term "emerald" comes from Vulgar Latin: esmaralda/esmaraldus, a form of Latin smaragdus, which was a via Ancient Greek: o (smáragdos; "green diamond") from a Semitic language. Old French: esmeraude and Middle English: emeraude.  The term "emerald" was first used, according to Webster's Dictionary, in the 14th century. 

 

Emeralds are rated using the four fundamental criteria—the four Cs of connoisseurship—as are other colored gemstones: color, clarity, cut, and carat weight. In grading colored gemstones, color is typically by far the most significant factor. However, clarity is ranked as a close second in the grading of emeralds. For an emerald to be regarded as a top gemstone, it must have a high degree of transparency in addition to the pure, verdant green hue specified below. 

The traditional "big four" gems are sapphire, diamond, ruby, and this member of the beryl family.