- 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.
- Nauru (Wikipedia)
Nauru (/nɑːˈuːruː/ nah-OO-roo or /ˈnaʊruː/ NOW-roo; Nauruan: Naoero), officially the Republic of Nauru (Nauruan: Repubrikin Naoero) and formerly known as Pleasant Island, is an island country and microstate in Micronesia, part of the Oceania region in the Central Pacific. Its nearest neighbour is Banaba of Kiribati about 300 km (190 mi) to the east.