Colorless (D–Z scale) to fancy yellow, pink, blue, green, and brown, exhibiting adamantine luster and 0.044 dispersion.
Chemical formula
C (Isometric Crystalline Carbon)
Other Gemstones • Opal (Hydrated Amorphous Silicaoid)
Opal
White, dark/black, crystal, or orange-red body color displaying spectral 'play-of-color' (flashes of red, green, blue, and violet) caused by diffraction of light through uniform three-dimensional grids of silica spheres.
SiO₂ · nH₂O (Hydrated Silicon Dioxide containing 3–10%+ water)Mohs 5.5 – 6.5 Mohs
Mineralogical & Gemological Profile
| Mineral Family | Other Gemstones |
|---|---|
| Mineral Species | Opal (Hydrated Amorphous Silicaoid) |
| Gemological Variety | Precious Opal & Fire Opal |
| Chemical Composition | SiO₂ · nH₂O (Hydrated Silicon Dioxide containing 3–10%+ water) |
| Crystal System | Amorphous (Mineraloid composed of stacked silica nanospheres) |
| Mohs Hardness | 5.5 – 6.5 Mohs |
| Specific Gravity | 1.98 – 2.25 |
| Refractive Index | 1.370 – 1.470 (Singly refractive) |
Color Characteristics & Optical Behavior
White, dark/black, crystal, or orange-red body color displaying spectral 'play-of-color' (flashes of red, green, blue, and violet) caused by diffraction of light through uniform three-dimensional grids of silica spheres.
Geological Context & Pakistani / Global Localities
Forms from low-temperature silica-bearing solutions in sedimentary sandstones/claystones (Australia) or volcanic tuffs/rhyolites (Ethiopia, Mexico).
Collector Interest & Rarity Factors
Solid precious opals showing broad harlequin, ribbon, or rolling flash play-of-color across the entire dome.
Fine Jewelry Applications
Protective bezel-set pendants, earrings, and occasional-wear rings.
Treatment Considerations & Disclosure
Solid natural opals must be clearly distinguished from assembled doublets/triplets, sugar-acid or smoke-treated matrix opals, and hydrophane opals (which absorb water and liquids). Synthetic Gilson-type opals are also disclosed.
Care & Cleaning Instructions
Requires special care: never immerse hydrophane (Ethiopian) opal in oils, perfumes, or colored liquids; avoid extreme dryness, heat, and ultrasonic cleaners. Wipe with a slightly damp soft cloth.
Traditional Meaning
Traditional Symbolism & Cultural Heritage
Admired by Roman naturalists as combining the fire of ruby, the purple of amethyst, and the sea-green of emerald. Official October birthstone.
Note: Cultural and birthstone traditions are presented strictly as historical folklore, never as scientifically verified medical or metaphysical effects.
Other Gemstones
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Chemical formula
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Chemical formula
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