Concept information
Preferred term
opal
Definition
- 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 its amorphous property, 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. (Adapted from: https://en.wikipedia.org/wiki/Opal)
Broader concept
In other languages
-
French
-
opaline
URI
http://data.loterre.fr/ark:/67375/QX8-RZG1KB9B-Z
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