I've recently started playing 5e (as my and most of the players' first DnD game) and at one point my Transmutation specialist Wizard used the Minor Alchemy class ability (PHB, p. 119) to turn some stone into wood. While thinking about this ability and its implications, we started wondering if the default "wood" that gets created is from a particular type of tree, and for that matter, whether the caster can decide what kind of wood it's going to be. For example, could you intentionally create some cedar, or rich mahogany?
Presumably copper or iron are pure samples of their respective elements, but the idea of "pure wood" seems non-obvious, as does stone (which stone?) Have any rules for determining the types of materials created by transmutation been established, either in the fifth or previous editions?