What is it?
Emerald is a gemstone and a variety of the mineral beryl (Be3Al2(SiO3)6) colored green by trace amounts of chromium and sometimes vanadium.
Where is it found?
The principal Emerald deposits are currently mined in Colombia, Brazil, and Zambia.
Chemistry of beryl
Beryl (Be3Al2Si6O18) have six-membered rings of tetrahedra with ideal formulas Si6O18, and used to be classified as cyclosilicate. However, more recent classifications sometimes treat it as tectosilicates.
The picture below shows a single unit cell of beryl.
The yellow Si tetrahedra are in the upper layer, the green ones in the lower layer. The outer points of the tetrahedra are actually edges viewed along their length. The purple tetrahedra contain Be and are viewed down their four-fold inversion axes. The solitary blue atoms are Al, in 6-fold coordination with the adjacent tetrahedral oxygens.
Reference: en.wikipedia.org ~ multicolour.com ~ gemselect.com ~ minerals.net ~ uwgb.edu ~ gemsociety.org
Emerald is a gemstone and a variety of the mineral beryl (Be3Al2(SiO3)6) colored green by trace amounts of chromium and sometimes vanadium.
Name
The word "Emerald" is derived, from Vulgar Latin: Esmaralda/Esmaraldus, a variant of Latin Smaragdus, which originated in Greek: σμάραγδος (smaragdos; "green gem").
Grading
Emeralds, like all colored gemstones, are graded using four basic parameters:
- Color: Emeralds occur in hues ranging from yellow-green to blue-green, with the primary hue necessarily being green.
- Clarity: Emerald tends to have numerous inclusions and surface breaking fissures. Their clarity is graded by eye.
- Cut
- Carat weight
color is by far the most important criterion.
Properties
Formula: Be3Al2(SiO3)6
Formula: Be3Al2(SiO3)6
Molecular Mass: 537.50
Density: 2.67 to 2.78
Density: 2.67 to 2.78
Hardness: 7.5-8 on the Mohs scale
Crystal symmetry: Dihexagonal Dipyramidal
Color: Green shades to colorless
Where is it found?
Colombia arguably produces the finest Emeralds. As a general rule, Brazilian Emeralds tend to be darker in tone and more heavily included.
Use
It is used in all forms of jewelry, and less transparent stones are cut into cabochons.Chemistry of beryl
Beryl (Be3Al2Si6O18) have six-membered rings of tetrahedra with ideal formulas Si6O18, and used to be classified as cyclosilicate. However, more recent classifications sometimes treat it as tectosilicates.The yellow Si tetrahedra are in the upper layer, the green ones in the lower layer. The outer points of the tetrahedra are actually edges viewed along their length. The purple tetrahedra contain Be and are viewed down their four-fold inversion axes. The solitary blue atoms are Al, in 6-fold coordination with the adjacent tetrahedral oxygens.
History and Myth
The emerald has long been known as the jewel of Kings, its rarity and beauty lending itself well to possession by royalty. As a talisman, it was said to have the ability to sharpen the wits, confer riches and power and to predict future events. The emerald was also used as an antidote for poisons and infected wounds, as well as against possession by demons. The soothing green color of the emerald was thought to be restful to the eyes when they had been under much strain.
The emerald has long been known as the jewel of Kings, its rarity and beauty lending itself well to possession by royalty. As a talisman, it was said to have the ability to sharpen the wits, confer riches and power and to predict future events. The emerald was also used as an antidote for poisons and infected wounds, as well as against possession by demons. The soothing green color of the emerald was thought to be restful to the eyes when they had been under much strain.
Reference: en.wikipedia.org ~ multicolour.com ~ gemselect.com ~ minerals.net ~ uwgb.edu ~ gemsociety.org
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