Opals

Gem quality opal is one of the most spectacular gemstones. The best opals can command prices per carat that rival the most expensive diamonds, rubies and emeralds. They are very popular gems. The internal structure of precious opal makes it diffract light; depending on the conditions in which it formed it can take on many colors. Precious opal ranges from clear through white, gray, red, orange, yellow, green, blue, magenta, rose, pink, slate, olive, brown, and black. Of these hues, the reds against black are the most rare, whereas white and greens are the most common. It varies in optical density from opaque to semi-transparent.

  

From fire opal to white opal - LINK

Rough opal stone mined at Coober Pedy Opal Fields - LINK

Magdalena mining district in Jalisco, Mexico - LINK

Koroit Boulder Matrix Opal - LINK

Lightning Ridge rough Opal Nobby 62 ct Gem - LINK

White Ethiopian opal - LINK

Discovered in 1989, this is one of the largest (2765 carats) and finest quality boulder opals ever mined. This opal is unique not only for its size but also for its quality---every color of the spectrum is visible which is extremely rare, even in the finest of opals. - LINK

Photo credit: Jessica Hately

Blue crust opal - LINK

Boulder opal. Photo by ozplasmic on Deviantart

1151 gr or 5755 ct One of the Largest Black Opal from Grawin - LINK

Rough opal - LINK

Display at the Cullen Hall of Gems and Minerals. Photo by Ed T on Flickr

Welo opal - LINK

Opal from Wollo, Ethiopia - LINK

Opal nodule.Wolfgang E. Henkel collection - LINK

Yowah matrix opal - LINK