Iron Sulfide Grains Produced by Coalescence of Fe and S Smoke Grains.

A new experimental method for preparing ultrafine iron sulfide grains is proposed. Troilite, marcasite and pyrrhotite grains predominantly, were produced by the coalescence between solid iron grains and liquidus sulfur grains at temperatures above 100°C. Troilite and marcasite grains were grown as single crystals of a complicated polyhedral shape. Pyrrhotite grains exhibited a typical DDSS (diffusion-dependence shell structure) shape produced by the diffusion of iron atoms to the surface layer. Iron grains covered with a thin sulfur layer were observed among the collected grains produced at the temperature of 50°C.