Solid opal

One (1) piece of opal that has been neither backed nor capped with any material by man.


Doublet opals

A composite of two (2) pieces, consisting of a slice of opal cemented onto a base material. Usually natural opal is used, however synthetic opal doublets also exist. Some examples of the base material are black potch, black glass, obsidian and boulder.


Triplet opals

A composite of three (3) pieces, consisting of a thin slice of opal cemented between a black/dark base material and a clear top layer.  Common top layers for triplets are glass, quartz and plastic.


Black opal

Is precious opal that when viewed face up displays a play of colour on or within a black or very dark body tone (background).


Boulder opal

Is Natural opal type 2 Is where the precious opal is naturally attached to the host rock in which it was formed. The host rock, normally ironstone or quartzite is of a different chemical composition to the precious opal.

Crystal opal

This term refers to the diaphaneity of the stone, not it’s structure.It is translucent to transparent. Precious crystal opal displays a play of colour on or within this translucent to transparent bodytone (background).


Style of cutting as opposed to faceting it refers the dome shape of the stone, described as low, medium or high.


Describes the shape of the cut stone. It is as any shape other than oval or round.

Undulating opal

The piece may be conventional in shape or freeform in shape the undulation gives reference to the nature of the surface of the piece- hence freeform undulating or oval with undulating surface

Carved opal

Opal having an undulated surface, free in shape, may be figurative and representative to abstract.

Artificial opal

technically has three sub categories; SYNTHETIC OPAL, IMITATION OPAL AND COMPOSITE OPAL.

Synthetic opal

Opal created by man having essentially the same chemical and physical properties as it’s natural counterpart.Examples are Gilson, Inamori, Kyocera.

Imitation opal

Material that resembles opal but has different chemical, physical and gemmological properties to that of natural opal.
Imitation opal may be either natural material or synthetic material. Some examples are Paua Shell, Ammolite, Plastic, Glass, and Polymer and silica mixture.

Composite opal

Usually laminates that may be made from natural, synthetic or imitation opal cemented onto base materials described as doublet, triplet or mosaic.