What Is Odontolite? The Blue Turquoise Lookalike in Antique Jewellery

Some blue cabochons in antique jewellery may look like turquoise but consist of a different material. Odontolite is one historical example. It is associated with fossil dentine and was also marketed under names such as bone turquoise, which can easily cause confusion.

The historic brooch investigation

SSEF’s 2012 article describes six brooches containing mostly odontolite, along with some actual turquoise and glass. Microscopic examination and Raman analysis helped separate the materials. The finding shows why matching colour across a jewel does not prove matching identity.

How odontolite becomes blue

Odontolite contains mainly fluorapatite. The article explains that heating can change the state of manganese traces and create a blue appearance. This is different from simply assuming that every turquoise-coloured material is the mineral turquoise.

Surface pores, banding and, in some specimens, features associated with ivory structure contributed to the investigation. Such observations are part of a laboratory assessment, rather than a guaranteed visual rule for every blue antique stone.

Why antique settings need careful reports

Ask whether each relevant stone was examined or whether only selected pieces were tested. An old object can contain original stones, substitutions or a mixture of materials. Mineral identity does not independently establish the age or complete ownership history of a jewel. Keep the findings tied to the specific stones and questions addressed by the report.

Sources and further reading

SSEF Swiss Gemmological Institute, Facette, issue 19, January 2012, pp. 16-17, “Odontolite & Heat Treatment of Apatite; The Blue of Odontolites vs. the Blue of Apatites”. 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.