Crystal Opal

Chemical Formula

SiO₂ · nH₂O

Color

White, Colorless, Blue, Red, Green, Yellow, Orange, Brown, Pink, Purple, Gray, Black, Banded, Multicolored

Hardness

5.5 - 6.5

Crystal System

Amorphous

Refractive Index

1.37 - 1.47

SG

1.98 - 2.25

Transparency

Transparent to translucent

Double Refraction

None

Luster

Vitreous, pearly, waxy

Cleavage

None

Mineral Class

Opal