FIG. 6. Compositional variations of laurite grains, Ir vs. As and Ir vs. Os. Lines of calculated correlation and correlation coefficients, r, are shown. Open circles = Pontyn samples, solid circles = Tambanio samples. (a) Iridium vs. As, (b) Iridium vs. Os, (c) Arsenic vs. Se, (d) Osmium vs. As.