The mine spirit of the Saxon and Bohemian workings was not decoration. It was the name for a set of real and lethal hazards in a place where nobody yet had the vocabulary of gas chemistry, and reading it as superstition misses what it was doing.
Underground there is air that ignites and air that kills without any warning at all, the conditions English pits later called firedamp and blackdamp. There are ores that look valuable, yield nothing on smelting and poison the smelter with arsenic fumes while they fail. There are roof falls that come with no sound before them. A being who inhabits the workings, who resents carelessness and disrespect, who moves the good ore and substitutes bad, and who has to be placated is a compact and reasonably accurate operating model of that risk, expressed in the only terms available to the men working it.
The naming survives in two places on the periodic table. The kobold and cobalt are described elsewhere on this page. The second case is nickel. Kupfernickel, the copper spirit's ore, was the mineral that looked like a copper ore and refused to give up any copper, and the name is the same mocking spirit in another form. The metal eventually isolated from it kept the second half of the insult and nothing else.
Paracelsus's own Latin for these beings is pygmaei as well as gnomi, which quietly imports the dwarf race of classical geography into a Renaissance mining cosmology. It is a useful reminder of what he was doing. The miners had the observations. The scheme of four, and the symmetry that required an earth being to stand beside a water being and an air being, was his.