Beryl – Emerald

Description:

Emerald is a variety of the mineral species beryl (BARE-ul); hexagonal crystal system.

Appearance:

• transparent; highly included stones may be translucent
• light to very dark green to very strongly bluish green

Identification:

Refractive Index: 1.577-1.583 (+-.017)
Absorption Spectra: distinct lines at 683 and 680.5 nm, less distinct lines 662 and 646, partial absorption between 630 and 580 nm and almost complete absorption of the violet
Cause of Color: usually chromium; some are colored by vanadium, or by both chromium
and vanadium 
Specific Gravity: 2.72 (+.18,-.05)
Hardness: 7 1/2 to 8 ; Toughness: poor to good

Stone Information from:

Gem Reference Guide, by GIA, ISBN 0-87311-019-6
Gemstones of the world, Third Edition, by Walter Schumann, ISBN 1-4027-4016-6
https://www.gemdat.org/gem-1375.html
https://www.mindat.org/min-1375.html