From the book itself:

Bronze Jikkit (the Bronze Bloom)
Biome: Subterrene
Diet: Metals and ores
Aggressive?: No (unless in possession of metal objects)
Rarity: *
Type: Flora (Underground)

"Unlike other jikkit vines (which are similar to regular-yet-sentient plants), the bronze jikkit lives only in caves. They survive by extending to great lengths so they can find metallic ore to devour. They are considerably more common than silver or gold jikkits (and live in more accessible locations), but they are still rare nonetheless. (My jikkits do not officially have names, per se, but my bronze one mainly responds to "Bert.)"

So, it's a plant that eats ores. This one eats mostly any ore, but you can probably tell what its favorite meal is...