Emerald
Emerald derives it's name from the Greek Smaragdos, which, in turn, probably came
from Persia. It means "green stone" and, in ancient time, referred not only to emeralds,
but also to most green stones.
Emerald, along with aquamarine and beryl, belong to the Beryl group, being the most
precious of the group. Its green is incomparable, and it's therefore called "emerald green" (not
only in mineralogy). The pigment comes from chrome and sometimes vanadium. The color is very resistant to light and heat, and only alters at 1292-1472F/700-800C.
- Color : Emerald green, light green, yellow-green, dark green
- Color of streak : White
- Mohs' hardness : 7 1/2-8
- Specific gravity : 2.67-2.78
- Cleavage : None
- Fracture : Small conchoidal, uneven, brittle
- Crystal system : Hexigonal (trigonal); hexigonal prisms, columnar
- Chemical composition : Al2Be2(Si6O18) aluminium berylium silicate
- Transparency : Transparent to opaque
- Refractive index : 1.576-1.582
- Double refraction : 0.006
- Dispersion : 0.014
- Pleochroism : Definate; green, blue-green to yellow-green
- Absorption spectrum : 6835, 6806, 6602, 6460, 6370, (6060),
(5940), 6300-5800, 4774, 4725