That thing that gets many folks mixed up is some words like sun, July, ect are used in songs, but not when the characters are talking outside of songs. It is easy to mix the 2 together and think they do use terms like ice, July, ect. As far as I remember they use hard water, not ice, for example.
Sky stones, maybe cloud stones, not sure if they'd have a special word like gravel or not.
Pyroclastic flow they may call burning smoke, fire smoke or something like that. In an episode of the tv series I recall Littlefoot calling a pool of lava bubbling fire. I don't recall if that was during a song or regular conversation. I'd have to get the dvd and look at the episode.