Micro-CT Pearl Testing: Seeing Internal Growth in Three Dimensions

The outside of a pearl can look convincing while its centre holds the most useful identification clues. X-ray microtomography, often called micro-CT, helps laboratories examine these hidden structures in three dimensions without cutting the pearl open.

From a flat image to virtual slices

A conventional radiograph projects internal features onto a flat image. Structures can overlap in that view. Micro-CT uses multiple X-ray views to reconstruct the interior, allowing the analyst to inspect virtual sections in different directions.

SSEF’s 2009 article describes how this approach helped investigate pearl growth features. It highlights difficult beadless cultured pearls, for which a clearer view of the central region can be particularly useful.

What can the images show?

Cavities, fissures and growth structures can become easier to understand when viewed from several angles. The analyst can ask whether a line belongs to one cavity or whether several different features overlap. This provides more context than judging a single dark shape in isolation.

Why interpretation still matters

A scan is not a label-making machine. Its usefulness depends on image quality, reference knowledge and careful interpretation of the whole pearl. The absence of an obvious bead does not prove natural formation. Ask whether the report gives a clear natural-or-cultured conclusion and whether additional investigation was needed for an ambiguous structure.

Sources and further reading

SSEF Swiss Gemmological Institute, Facette, issue 16, January 2009, pp. 8, “Micro x-ray-tomography displays growth features of pearls”. Read the original SSEF PDF.

This independent educational article explains historical SSEF research in original, simple English. It is not an SSEF publication. No source photographs or illustrations are reproduced.