Beryllium

Formula: Be3Al2(Si6O18)
Colour:  Colorless, green, blue, yellow, white, pink, etc.
Lustre: Vitreous, Sub-Vitreous, Waxy, Greasy
Hardness: 7½ - 8
Specific Gravity:  2.63 - 2.92
Crystal System: Hexagonal
            
              
 Name: Possibly from the Greek "beryllos" which referred to a number of blue-green stones in antiquity.