Black Opal is precious opal showing a play of spectral colours in dark body.

Light, Fire or Crystal Opal is precious opal with a body colour ranging from milky white to translucent.

Boulder Opal can be light or dark opal found in veins of ironstone.

Doublets are made by gluing slices of precious opal to a black backing.  The dark backing enhances the colours of the opal. Triplets are made by adding a clear protective cap of quartz or crystal glass to a doublet.