Features reported for this material
Opal
No crystal habit — nodules, seams and infillings.
amorphous
Play-of-colour where present; body tone runs black through white to transparent.
The drawing is a no crystal form. It does not grow as a crystal at all. Lumpy nodules, seams and infillings of rock. Compare it with what is in your hand as a prompt for better photographs, not as an identification. Waterwear, damage and incomplete growth can remove the expected form.
Editorial status: specialist review pending
Evidence record for this page
The links are editorial source targets, not certificates for a submitted stone. The page remains noindex until a named specialist checks the entry claim by claim.
- Handbook of Mineralogy, Mineralogical Society of America — mineral identity, crystal system, habit, physical properties, recorded localities.
- GIA Gem Encyclopedia and Gems & Gemology research — gem-variety terminology, trade context, reported sources, treatment context.
- GIA introduction to gem treatments — treatment categories, limits of visual treatment assessment, disclosure context.
- CIBJO Coloured Stone Commission, Official Gemstone Book — accepted nomenclature, artificial-product terminology, treatment disclosure terminology.
Author: pending · Specialist reviewer: pending · Review date: pending · Next review: pending
What it gets mistaken for
Opal is reported as being confused with doublets and triplets, synthetic opal and opalite glass. Photographs cannot resolve many of those alternatives. If you are not certain, say so and preserve the name you were originally given as a seller claim.
Also traded as: black opal, boulder opal, crystal opal, fire opal.
Where it comes from
Reported producing localities in this working reference include Australia, Ethiopia, Mexico, Brazil, Indonesia. This is not proof that a stone came from one of them, and it does not mean an approved purchase route exists there.
Treatment
Smoke and sugar treatment of Ethiopian material; doublets and triplets are assembled and excluded as composites.
Tell us what has been done to it, if you know, and distinguish what you know first-hand from what somebody told you. Media cannot establish treatment. Any acceptance policy and laboratory requirement is decided for the case.
How to photograph it
Ethiopian hydrophane opal absorbs water and CHANGES APPEARANCE while it is wet, so the wet-and-dry advice we give for everything else actively misleads on this one species. Photograph opal dry, in daylight, and tell us if it has been wet recently. The desk knew this and the page did not say it.
Daylight, on a plain white surface, and photograph it dry. This can reveal different apparent surface and internal features without proving identity, quality or value. Put a ruler or another clearly identified scale reference in the frame. The full guide is here.