Emerald

An emerald is a mineral gemstone and a variety of beryl. It is the birthstone of someone whose birthday is in the month of May. It is a green crystal. The emerald is one of the most valuable gems, along with the ruby, the opal, topaz, the diamond, and a sapphire.

Emerald
Emerald crystals from Muzo, Colombia
General
CategoryBeryl variety
Formula
(repeating unit)		Be3Al2(SiO3)6
Crystal symmetry(6/m 2/m 2/m) – Dihexagonal Dipyramidal
Unit cella = 9.21 Å, c = 9.19 Å; Z = 2
Identification
Molecular mass537.50
ColorGreen shades
Crystal habitMassive to well Crystalline
Crystal systemHexagonal (6/m 2/m 2/m) Space group: P6/mсc
CleavageImperfect on the [0001]
FractureConchoidal
Mohs scale hardness7.5–8
LusterVitreous
StreakWhite
DiaphaneityTransparent to opaque
Specific gravityAverage 2.76
Optical propertiesUniaxial (-)
Refractive indexnω = 1.564–1.595,
nε = 1.568–1.602
Birefringenceδ = 0.0040–0.0070
Ultraviolet fluorescenceNone (some fracture filling materials used to improve emerald's clarity do fluoresce, but the stone itself does not)
References[1]

Etymology

The word emerald comes from Vulgar Latin. The word was Esmaralda/Esmaraldus, a different way of saying the Latin word Smaragdus, which came from the Greek, σμάραγδος (smaragdos; "green gem").[2][3] It first came from a Semitic word, izmargad (אזמרגד). This meant "emerald" or "green".[2] The name could also be related to the Semitic word baraq (בָּרָק ;البُراق; "lightning" or "shine") (c.f. Hebrew: ברקת bareqeth and Arabic: برق, barq, "lightning"). It is where the Persian (زمرّد zomorrod), Turkish (zümrüt), Sanskrit (मरग्दम् maragdam) and Russian (изумруд; izumrúd) words came from.[3]

References
  1. "Emerald at Mindat". Mindat.org. 2010-07-19. Retrieved 2010-07-30.
  2. Fernie M.D., W.T. (1906). Precious Stones for Curative Wear. John Wright. & Co.
  3. "Online Etymology Dictionary". etymonline.com. Retrieved 15 April 2010.
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