In this question, it was decided a goblin could be permanently True Polymorphed into a lump of adamantine. True Polymorph can also turn a goblin into a larger creature, like a cow. This effectively increases the mass of the goblin.
If a wizard were to turn said goblin (poor, poor Squee) into a lump of adamantine, can the wizard specify how large a lump he gets? Are there any limitations on how large it could be? For example, can the goblin become:
- A large boulder-sized hunk of adamantine
- A dragon-sized hunk of adamantine
- A mountain-sized hunk of adamantine