Interludium: Of Dwarves
Regarding the building and excavating of the dwarven cities, Gimli's comments on the glittering caves of Aglarond make me think that dwarves tended stone and mountains not unlike elves may have tended trees.
Gimli talks of the growth of stone, and the various compositions of minerals which all demand unique care.
Speculative as this may be, but I can well imagine dwarves calculating the further growth of ore veins and then using the least possible physical force on it while still achieving maximum excavating effect.
And who knows what else they may have used on stones and minerals: chemicals? Dwarf-magic
? Or did they 'only' have a method of finding existing underground caves and caverns from above or from a distance, and then only used and customized the caves?
Ah, listen to them... the children of the night... what sweet music they make...