No, it's actually a form of silica.
yes
Its a rock. Just a shiny one.
Neither. Opal is a mineraloid, as it does not have a sufficiently organized structure to be considered a mineral.
igneous
opal
Opal is amorphous mineraloid, occurrence : Sedimentary and secondary from the alteration of high silica igneous extrusive rocks
Opal is not considered a rock but actually a mineraloid gel. It is deposited at relatively low temperatures. One of the characteristics if igneous rocks, sometimes called fire rocks, is that they are formed at high temperatures. Whether an igneous rock forms below ground, or on or near the surface, it's all about heat forming the rock. Opal cannot take its form under that kind of heat.
Opals are a mined substance that can be found in fissures in rock. It is then processed, cleaned up and cut down to make different types of jewelry. This is how opal ware is made.
The types of Opal that i am familiar with are White Opal, Fire Opal, Boulder Opal, Black Opal, Crystal Opal, Light Opal, Doublet Opal, Triplet Opal, Common Opal, Synthetic Opal, and Immitation Opal.
Opal is neither a sedimentary, igneous, nor metamorphic rock. It is actually a mineraloid composed of hydrated silica that is formed from silica-rich solutions at low temperature, often found in sedimentary rocks like sandstone or volcanic areas.
There are 5 basic types of opal. These types are Peruvian Opal, Fire Opal, Girasol Opal, Common opal and Precious Opal.
An opal is considered to be a mineraloid, meaning that it has all of the properties of a mineral-- solid, inorganic, naturally forming, has a chemical composition-- but does not demonstrate crystallinity. Other examples of mineraloids include obsidian, an amorphous glass (that is not a crystal).