There are a few different types of opals; Black/Dark Opal, Light/White Opal, Boulder Opal, Matrix Opal, Composite Natural Opal, fake as fake can be opal, and deceiving opal doublets and triplets.
Opals are formed from rain, formed when water seeps down into crevasses and picks up silicon dioxide on the way. Over time the rock, evaporates, and leaves behind what will become this beautiful and colorful gemstone. Some opals need to dry out a bit or else crazing can occur, which are cracks in the opal.
Play of Color- This refers to the rainbow like colors within an opal. Some refer to it as its flash, because its like a flash of light similar to a prism in a window.
Fun facts- the 14th anniversary gemstone. Opals have been popular among Royalty; The crown of the Holy Roman Emperor has a fiery red Opal called “The Burning of Troy”, which was given as a gift from Napoleon to Josephine, and not exist in the crown jewels of France. Queen Victorias favorite wedding gift were opals.
Care of Opals- Opals are a softer stone, therefore it is important to be cautious with wearing them in rings. In general you do not want avoid hot temperatures and any chemicals they may come in contact with.
For your sake I will highlight my favorite Opals and briefly discuss the rotten ones.
Major sources; Australia, Ethiopia, Brazil (the ones below are from my favorite sources of each type)