Interference colour inside a yellow stone
A 2025 GIA note describes a 6.28-carat yellow cushion-cut sphene. It showed strong fire and doubled features. Its refractive index was above the instrument’s range, so Raman analysis identified the material. Growth features, healed fissures and particles formed a scene inside the stone. Oblique fibre-optic light revealed colourful interference in part of that scene. The account describes this appearance as soap bubbles.
The phrase describes an appearance. It does not mean that gas bubbles are trapped in the stone. The account ties the view to its lighting and laboratory work. A rainbow photographed at one angle is not the stone’s lasting body colour. It does not tell us if the stone was treated or where it came from. This way of reading keeps both the striking light effects and the less obvious features inside the stone in one account.
Read alongside: Soap Bubbles in Yellow Sphene.
The surface is a record too
John Koivula’s 2016 account concerns a small green titanite crystal linked to Russia’s Ural Mountains. Energy-dispersive X-ray fluorescence linked vanadium to the green colour of that specimen. Differential-interference-contrast microscopy showed fine growth features on its surfaces. The work concerns one crystal. It is not an explanation for every green titanite. Nor can an ordinary photograph reproduce those tests.
The account shows why rough and polished objects answer different questions. Polishing can remove natural surface traces of growth. A faceted gem may show beautiful optics but no longer retain that visible surface history. Check whether a collection record describes a natural face, a polished face or an internal view. A feature on the surface need not be an inclusion or something found in every cut stone.
Read alongside: Crystal Growth Features in Titanite.
Compare like observations
When comparing fire, body colour and microscopic interference, keep the viewing angle and lighting beside each observation.
Read alongside: A source map is a guide, not a passport.