Crystal opal stones are generally considered to be transparent
opal of sea blue colours, but this category of crystal opals has multi fire crystal
opals that maybe be opaque to translucent, but the colours can be spectacular.
Deep tones of rich fire can give good effect in different lighting
so some people like crystal opals as a night stones as the opal can look
attractive under dim lights
South Australian opal fields are most prolific in supplying
crystal opals and Lighting Ridge in NSW also has deep strong fire crystal opals