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
Category	Beryl variety
Formula (repeating unit)	Be3Al2(SiO3)6
Crystal symmetry	(6/m 2/m 2/m) – Dihexagonal Dipyramidal
Unit cell	a = 9.21 Å, c = 9.19 Å; Z = 2
Identification
Molecular mass	537.50
Color	Green shades
Crystal habit	Massive to well Crystalline
Crystal system	Hexagonal (6/m 2/m 2/m) Space group: P6/mсc
Cleavage	Imperfect on the [0001]
Fracture	Conchoidal
Mohs scale hardness	7.5–8
Luster	Vitreous
Streak	White
Diaphaneity	Transparent to opaque
Specific gravity	Average 2.76
Optical properties	Uniaxial (-)
Refractive index	nω = 1.564–1.595, nε = 1.568–1.602
Birefringence	δ = 0.0040–0.0070
Ultraviolet fluorescence	None (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]

Related pages

• List of minerals
• Emerald (color)