Opal

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.

Back to Gems & Crystals →

Source: Wikipedia · Image: Wikimedia Commons · CC BY-SA 3.0

TOOTHJEWEL

Smile with sparkle — tooth gems, dental jewelry, safe application, and aftercare.

Get new guides by emailOccasional emails. No spam. Unsubscribe anytime.

InformationAbout Contact Privacy Policy Terms of Service Disclaimer Affiliate Disclosure Cookie Policy

Every entry, image, and fact is drawn from Wikipedia and Wikimedia Commons, used under public-domain and Creative Commons licenses. No content is AI-generated.