Beryl (beryllium aluminum silicate)
Types/Color
Aquamarine – light blue to blue-green
Bixbite – Red to strawberry-red
Emerald – Green
Goshenite – colorless
Heliodor – deep yellow
Morganite – Pink to peach
Other beryls may be referred to by their color, such as green beryl and yellow beryl.
Mohs hardness 7.5-8
Refractive index 1.57-1.6
Critical angle 39.5°
Specific gravity 2.65-2.75
Cleavage None
Fracture Conchoidal, tough
Dispersion Medium (.014)
Heat sensitivity None
Pleochroism Dichroic – Golden weak (yellow to light-yellow); Goshenite colorless, no dichroism; Green distinct (yellow-green to blue-green); Heliodor weak (gold-yellow to greenish-yellow); Morganite distinct (pale-pink to lavender-pink); Purple distinct (purple to colorless); Yellow (light yellow to medium yellow).
Birefringence (double refraction) Weak (.006-.009)
Crystal structure Hexagonal
Cutting Emerald and bixbite with heavy inclusions can break apart. Otherwise, beryl is probably the easiest stone to facet.
Polishing Beryl polishes easily with alumina or cerium oxide.