Does the radiation spectrum of bodies depend on it composition or not?

Question

In the second edition of Quantum Physics by Robert Resnick and Robert Eisberg, they write

"Matter in a condensed state (i.e., solid or liquid) emits a continuous spectrum of radiation. The details of the spectrum are almost independent of the particular material of which a body is composed, but they depend strongly on the temperature."

But just one page later, they write,

"Generally speaking, the detailed form of the spectrum of the thermal radiation emitted by a hot body depends somewhat upon the composition of the body."

Does this mean that bodies' emission spectrums are more dependent on temperature for lower temperatures and that at higher temperatures composition begins to matter? Or is there something I'm missing?

Answer 1

If a solid object is hot enough to glow dull red, then its emission spectrum will be that of a black body, or nearly so and what it is made of will not matter.

If it is at room temperature, then its emission spectrum will depend on what it is made of (gold, silver, copper, sulfur, iodine, carbon, etc.)

Between these extremes, both spectra will be present, superimposed on each other.

An important special case is that of materials like rare-earth oxides (in particular, thoria) which, when heated with a flame, become participants in the combustion process and hence can reach very high temperatures through a mechanism called candoluminescence. In this state they become brilliantly luminescent, much more so than the flame heating them.