Green-Blue Black Opal from Lightning Ridge in Freeform

About Black Opal

Black opal is opal with a dark grey, brown or black body tone; the body colour does not itself guarantee strong play-of-colour. Its flashes arise when regularly arranged microscopic silica spheres diffract light, producing shifting patches of blue, green, yellow, orange or red. The material is hydrated, amorphous silica rather than a crystal, with variable water content. It ranges from translucent to opaque, and an even dark…