Opal
Opal (Mineraloid) · Precious Gemstone
Crystal System
Amorphous
Mineral Group
Mineraloid (Silicate family)
Chemical Formula
SiO2·nH2O
Formation Process
Sedimentary or volcanic deposition from silica-rich solutions at low temperatures
About This Crystal
The specimen is set into a gold-toned metal chain necklace, featuring a distinct faceted or cabochon-cut elongated oval shape showing a brilliant play-of-color with flashes of pink, blue, green, and orange against a pale translucent body.
Physical Characteristics
White to light translucent body color with vivid multi-color spectral flashes, white streak, conchoidal fracture, no cleavage, specific gravity around 2.10 to 2.20, brittle tenacity, and often exhibits greenish-white fluorescence under UV light.
Optical Properties
Isotropic (amorphous structure), refractive index ranging from 1.370 to 1.470, exhibits pronounced play-of-color caused by the diffraction of white light through its ordered microscopic silica sphere grid.
Hardness & Durability
Origin Region
Australia, Ethiopia, Mexico, and the United States
Hardness & Durability
Mohs hardness of 5.5 to 6.5, making it relatively soft and susceptible to scratching; poor toughness due to internal water content making it prone to crazing or cracking under sudden temperature changes.
Care & Maintenance
Clean gently with warm soapy water using a soft cloth, avoid ultrasonic cleaners, steam cleaners, harsh chemicals, and extreme dryness or direct prolonged heat sources which can cause the stone to craze or lose water.
Rarity & Value
Rarity ranges from common to very rare depending on the intensity of the play-of-color, transparency, and geographic origin; precious opals with strong fire can command high market values.
Special Characteristics
Exhibits a striking play-of-color resulting from the regular arrangement of microscopic silica spheres that diffract light into spectral colors.
Lore & History
Historically associated with hope, innocence, and purity by ancient Romans and Greeks, who believed it possessed the magical powers of all precious stones combined; often linked to the crown chakra in modern metaphysical traditions.