Golf balls having core structures with iron-containing centers

A multi-layered golf ball, comprising:

• i) an inner core comprising a metal powder dispersed in a thermoset or thermoplastic polymeric matrix, the metal powder comprising particles having a weight average size in the range of about 10 μm to about 450 μm, the inner core having a center and outer surface, and a diameter in the range of about 0.100 to about 1.100 inches;
• ii) an outer core layer comprising a thermoset or thermoplastic material, the outer core layer being disposed about the inner core and having a thickness in the range of about 0.200 to about 0.800 inches, wherein the inner core has a specific gravity (SGinner) and a center hardness (Hinner core center), and the outer core has a specific gravity (SGouter) and an outer surface hardness ((Houter surface of OC), the SGinner being greater than the SGouter, and the Hinner core center being in the range of about 10 to about 80 Shore C and the Houter surface of OC being in the range of about 65 to about 96 Shore C to provide a positive hardness gradient across the core assembly;
• and
• iii) a cover having at least one layer disposed about the multi-layered core.