Nevada black opals' play of color fire is the tops. Few sights compare to a large black opal in your hand with the sun over your shoulder.
This super gem specimen did not dry well after it's dome froze and broke. I will make a big bead pendant out of this later. 
This black dried without a crack. Dense dark opal with fluid colors on a light skin in a natural arrowhead shape. Bright pure colors of blue and violet under the green, & red with yellow shooting flames. 2 1/4" by 2 1/2" by 1/2" $10,500. (Krol's)
color close up wet