Odontolite

Much Odontolite, or "Occidental Turquoise" is fossilized bone or teeth consisting of microcrystalline apatite. It is frequently mis-identified as turquoise, and the majority (if not all) of "turquoise replacements" of fossils are likely to be odontolite rather than turquoise. Originally thought to be coloured by vivianite, or perhaps by copper salts, recent research has suggested that the original material was fossilized mastodon ivory found in Miocene geological layers next to the Pyrenean chain, France - which had been heated to induce the blue colour change. The original material is almost entirely fluorapatite, with traces of Fe, Mn, Ba and U. Odontolite owes its turquoise-blue color to Mn#5+# ions in a distorted tetrahedral environment of four O#2–# ions (Reiche et al., 2001).