opal
Sign in to savethumb|alt=A map of the world displaying the countries where opal is most commonly found; Australia, Ethiopia, Brazil, Mexico and the United States of America are highlighted.|Main opal producing countries
AI overview
Opal is a gemstone prized for its distinctive play of colors and is mined in several countries around the world, with Australia, Ethiopia, Brazil, Mexico, and the United States being the primary producers. It matters because it is valued as a precious stone used in jewelry and decorative items.
AI-generated from the Wikipedia summary — may contain errors.
Key facts
- Mineral.fluorescence
- black or white body color: inert to white to moderate light blue, green, or yellow in long and short wave, may also phosphoresce, common opal: inert to strong green or yellowish green in long and short wave, may phosphoresce; fire opal: inert to moderate greenish brown in long and short wave, may phosphoresce
- Mineral.absorption
- green stones: 660 nm, 470 nm cutoff
- Mineral.streak
- White
- Mineral.density
- 2.09 g/cm3
- Mineral.diagnostic
- darkening upon heating
- Mineral.solubility
- hot salt water, bases, methanol, humic acid, hydrofluoric acid
- Mineral.diaphaneity
- opaque, translucent, transparent
- Mineral.name
- Opal
- Mineral.category
- Mineraloid
- Mineral.boxbgcolor
- 5cc4e7
- Mineral.image
- Opal-53714.jpg
Article
22 sectionsContents
- Precious opal <span class="anchor" id="Precious_opal_anchor"></span>
- Common opal
- Varieties of common opal
- History
- Sources
- Australia
- Ethiopia
- Virgin Valley, Nevada
- Mexico
- Other locations
- Fossil opal
- Synthetic opal
- Local atomic structure
- Microcrystalline opal
- Noncrystalline opal
- Opal surface chemical groups
- Etymology
- Historical superstitions
- Examples
- See also
- References
- External links
thumb|alt=A map of the world displaying the countries where opal is most commonly found; Australia, Ethiopia, Brazil, Mexico and the United States of America are highlighted.|Main opal producing countries
Opal is a hydrated amorphous form of silica (SiO2·nH2O); its water content may range from 3% to 21% by weight, but is usually between 6% and 10%. Due to the amorphous (chemical) physical structure, it is classified as a mineraloid, unlike crystalline forms of silica, which are considered minerals. It is deposited at a relatively low temperature and may occur in the fissures of almost any kind of rock, being most commonly found with limonite, sandstone, rhyolite, marl, and basalt.