The GAA (Gemmological Association of Australia) in 1993
started Nomenclature which is a definition of this type of opal. The title
given to this type of opal is Black Dark Opal.
The Body tone chart has Dark opal set at rating of N5 to N7 while
Black opal has a body tone of N1 to N4.
Many buyers get confused between the Brightness chart and
the body tone chart. The brightness chart refers to the intensity of the play
of color while the Body Tone chart talks about the darkness of the body of the
This class of opal can be confusing but some of the
brightest opals to come out of the ridge are black dark opals with brilliant
fire and patterns. Opal is also a personal choice and different colours and
patterns appeal to certain buyers as if you’re looking for ring or pendant opal.
This category has the complete range of magnificent patterns
that the ridge is known for. The opal mined can be seam opal but also Nobbys
are found with incredible patterns and large percentage are cabochon so they
make ideal flashy fire ring stones and
represent good value.