Nevermind, found the correct answer: glow is due to oxides and chemical reactions AROUND the solid block of metal. However, the wiki article lists this effect as distinct from the black body spectrum of the object, and leaves the impression that even without it, the solid metal would glow more than a black body at those temperatures.

"Candoluminescence is the light given off by certain materials at elevated temperatures (usually when exposed to a flame) that has an intensity at some wavelengths which can, through chemical action in flames, be higher than the blackbody emission expected from incandescence at the same temperature.[1] The phenomenon is notable in certain transition-metal and rare-earth oxide materials (ceramics) such as zinc oxide, cerium(IV) oxide and thorium dioxide."

Whereas the wiki article for thorium says:

"A mantle glows brightly in the visible spectrum while emitting little infrared radiation. The rare-earth oxides (cerium) and actinide (thorium) in the mantle have a low emissivity in the infrared (in comparison with an ideal black body) but have high emissivity in the visible spectrum. **There is also some evidence** that the emission is enhanced by candoluminescence, the emission of light from the combustion products before they reach thermal equilibrium."