opal

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

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
Mineral.alt: A blue-green section of opal encased inside a light brown rock
Mineral.caption: A rich seam of iridescent opal encased in matrix
Mineral.formula: Hydrated silica. SiO2·nH2O
Mineral.IMAsymbol: Opl
Mineral.color: Colorless, white, yellow, red, orange, green, brown, black, blue, pink
Mineral.habit: Irregular veins, in masses, in nodules
Mineral.system: Amorphous

via Wikipedia infobox

Wikidata facts

Image: Opal banded.jpg

Show 8 more facts

Commons category: Opal
chemical formula: SiO₂·nH₂O
Nickel-Strunz 9th edition (updated 2009): 4.DA.10
Nickel-Strunz '10th ed', review of (9th ed/ 2009 update): 4.DA.10
Commons gallery: Opal
IMA Mineral Symbol: Opl
described at URL: hedendaagsesieraden.nl/2023/04/10/opaal
Strunz 8th edition (series ID, updated): IV/D.01c

Sources (4)

via Wikidata · CC0

~27 min read

Article

22 sections

Contents

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

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.