gems, jade, pyroxene jade, fei cui, New Guinea, Papua New Guinea

A small stone artifact fashioned as a wood-carving gouge, discovered during an archaeological excavation on Emirau Island, has been determined to consist of jadeitite—jadeite jade. It is very unusual with respect to both pyroxene composition and minor mineral constituents. Pyroxene compositions lie essentially along the jadeite–aegirine join: Jd₉₄Ae₆ to Jd₆₃Ae₃₆, and without any coexisting omphacite. This contrasts with Jd-Di or Jd-Aug compositional trends commonly observed in jadeitites worldwide. Paragonite and albite occur in veins and cavities with minor titanite, epidote-allanite and zircon, an assemblage seen in a few jadeitites. Surprisingly, some titanite contains up to 6 wt% Nb₂O₅ with only trace Ta, and a single grain of a Y-Nb phase (interpreted as fergusonite) is present; these are unique for jadeitite. A possible source is along the Torare River in northeast Indonesia, from which samples of “chloromelanite” (actually jadeitite) were collected by C. E. A. Wichmann in 1903 near Humboldt Bay along with stone adzes fashioned from the same material.