Sliced into Spam and found firm white chunks embedded throughout. Is that mold or something bad

rises to the surface and solidifies as it cools, which can create the appearance of white spots. This is a natural occurrence in processed and cooked meats, especially those that are canned.
4. Visual Signs Your Spam Has Gone Bad
Visual cues that indicate that Spam may have gone bad include discoloration, such as a greenish or blackish hue, which can suggest mold growth. Additionally, a bulging can may indicate bacterial activity inside.
If the meat appears slimy or exhibits any unusual textures, these are also signs that the Spam