Opal: FL Blue-White SW
Hyalite Opal: FL Green SW
This specimen comes from Cedar Rim, a place about 35 miles from
Riverton, Wyoming. The fluorescent color of the hyalite opal is
from uranyl ion, one of the few activators that always fluoresces the
I don't know what the activator is in the blue-white fluorescing
The color scheme is reminiscent of willemite and margarosanite from
Franklin, though the dendritic opal does not fluoresce quite as
brightly as most margarosanite.
The specimen's display face is about 3 1/4 x 1 1/2 inches.
Opal is a type of amorphous, hydrated silica. In other words, it
doesn't have a regular crystal structure. Its empirical formula
is essentially the same as silicic acid, H2SiO3.
In the case of opal it's written as SiO2 nH2O.