1. opal
2. OpalOpal is an amorphous form of silica related to quartz, a mineraloid form, not a mineral. 3% to 21% of the total weight is water, but the content is usually between 6% to 10%. 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. Opal is the national gemstone of Australia, which produces 97% of the world's supply.
Read “Opal” on English Wikipedia
Read “オパール” on Japanese Wikipedia
Read “Opal” on DBpedia
Read “Opal” on English Wikipedia
Read “オパール” on Japanese Wikipedia
Read “Opal” on DBpedia
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