The art of revealing what is inside
A rough opal rarely delivers immediately what it holds. It is in the cutting that the stone reveals its personality: the lapidary must read the internal structure, identify how light behaves within the gem, and make decisions that will determine the character of the final piece. Few processes in jewelry demand as much judgment as opal cutting.
Types of opal cuts
Unlike diamonds and other hard gems, which are often faceted to maximize light reflection, precious opals are almost always worked into a cabochon format, a convex polished surface without facets. The curve of the cabochon amplifies opalescence.
- Simple cabochon: the most common form, flat base and convex top
- Double cabochon: convex on both sides
- Solid opal: cut from a single stone with no reinforcement, the most commercially valued form
- Doublet: a thin layer of opal bonded onto a dark base (obsidian or onyx) to imitate black opal
- Triplet: a layer of opal between a dark base and a transparent crystal cover
It is essential that buyers know how to distinguish between a solid opal and a doublet or triplet, as commercial value differs substantially. An ethical lapidary always discloses the nature of the piece.
How the lapidary reads a rough opal
Before any cut, the lapidary analyzes: play-of-color orientation, inclusions and fractures, color distribution, and optical layer thickness. The layer generating the play of colors must be preserved as much as possible.
Weight and proportion
In opal cutting, unlike diamonds, final weight is not always the priority. A lower cabochon may display cleaner, more uniform colors than a taller one. The finest lapidaries of Piauí have developed over decades a hereditary knowledge of local stones, forming part of the cultural heritage of Pedro II.
The relationship between cutting and design
For a contemporary jeweler, the conversation with the lapidary begins before the stone is finished. An opal is not a passive component: it sets the tone for the entire jewel. Working with opals demands openness to surprise and collaboration with the material itself. Rarely does the design come first; often, it is the stone that suggests what it wants to become.
Source: GOMES, C.B. et al. As Opalas do Piauí [The Opals of Piauí]. Brasília: CETEM/MCTI, 2025. Part of Fortes Jewellery's educational gemology series, based on scientific research by the Centro de Tecnologia Mineral of Brazil's Ministry of Science, Technology and Innovation.