Widmanstaetten Patterns in Josephinite, a Metal-Bearing Terrestrial Rock

Widmanstaetten patterns have been found in several specimens of josephinite, a complex, metamorphosed, metal-bearing rock from placers on serpentinized peridotite in southwest Oregon. The patterns, in interior less-altered regions of the specimens, are typical of exsolution textures produced during slow cooling of a homogeneous metal. The bulk composition of the metal phases indicates that the homogeneous metal must have existed at temperatures above 500°C. Josephinite Widmanstaetten patterns are the first known in terrestrial rock. We interpret them as further evidence that josephinite was derived from the mantle.