Depending on the conditions in which it formed, opal 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 black opals are the most rare, whereas white and greens are the most common.
|In November 1917 this mine produced the 1.5 pound precious Roebling Black Opal. The Opal was named after its owner Colonel Washington Augustus Roebling which is in the permanent collection of the same name at the Smithsonian Museum of Natural History.|