AMMO by MIG Pigments - Fine Pigment Powders for Modelling
Color: Metal Slag

From the Manufacturer:

Pigment powder of the highest quality, specially formulated by AMMO to get the best results. It can be used to represent the weathering effects commonly seen on spaceship engines in Sci-Fi films, as well as typical battle damages. Perfect for aircraft nozzles, vehicle engines and exhausts, and all types of tools as well. An essential color, always have one in your workbench!