Do coal miners work in underground caves?

No, of course not. They work in coal mines.

Caves don't develop in the Coal Measures.

Some 18-19C lead-miners in places like the Peak District (English Midlands) broke into or mined from natural caves in the area's Carboniferous Limestone. They were exploiting ore-bodies that had been intercepted by later cave development.

The iron-ore deposits in the Forest of Dean (England) did form within caves, but as a general rule caves and economic metallic ores do not otherwise co-exist.

Oh, and the adjective "underground" is tautologous!