OPAL

0.2 MICRONS

Grids of silica spheres 0.2 microns in size create red play-of-color flashes.

20% WATER

Opal contains up to 20% water trapped in its silica structure.
 

1829

The novel “Anne of Geierstein” gave opal a reputation of being unlucky.

FACTS

• Mineral: Hydrated Silica
• Chemistry: SiO₂•nH₂O
• Color: All colors
• Refractive index: 1.37-1.47
• Birefringence: None
• Specific gravity: 2.15 (+0.08, -0.90)
• Mohs Hardness: 5 to 6.5

source:gia.edu